Evolution of Gene Duplication in Plants

Comprehensive analysis of the stress associated protein (SAP) family and the function of PagSAP9 from Populus alba × P. glandulosa in salt stress

Poplar tree growth is frequently hindered by environmental stressors, particularly soil salinization. Enhancing salt tolerance is essential for improving their adaptability and biomass under these conditions. The Stress-Associated Protein (SAP) family, characterized by A20/AN1 zinc finger domains, plays a crucial role in plants' tolerance to abiotic stress. However, functional investigations on SAP proteins in poplar are limited. In our study, we identified 19 SAP members in poplar, distributed unevenly across ten chromosomes and classified them into two major groups based on phylogenetic relationship and structure characteristics. Notably, only three segmental duplications were found, while no tandem duplications were detected. The PagSAP9 gene from Populus alba x P. glandulosa, featured both A20 and AN1 domains, was successfully characterized and localized to both cytoplasm and nucleus. It was predominantly expressed in roots and leaves and showed significantly upregulation under salt stress. And the overexpressing PagSAP9 transgenic poplars enhanced the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), alongside reduced malondialdehyde (MDA) content. Additionally, DAB and NBT histological stainings further confirmed the positive effects of PagSAP9 gene. Collectively, these findings highlight the potential of the PagSAP9 gene to improve salt tolerance in poplar, emphasizing the broader applicability of SAP genes in plant stress resistance and providing valuable genetic resources for developing resilient plant varieties.

The physiological and molecular mechanisms of WRKY transcription factors regulating drought tolerance: A review

WRKY transcription factors (TFs) play crucial roles in responses to abiotic and biotic stresses that significantly impact plant growth and development. Advancements in molecular biology and sequencing technologies have elevated WRKY TF studies from merely determining expression patterns and functional characterization to uncovering molecular regulatory networks. Numerous WRKY TFs regulate drought tolerance in plants through various regulatory networks. This review details the physiological and molecular mechanisms of WRKY TFs regulating drought tolerance. The review focuses on the WRKY TFs involved in the phytohormone and metabolic pathways associated with the drought stress response and the multiple functions of these WRKY TFs, including biotic and abiotic stress responses and their participation in plant growth and development.

A 2OGD multi-gene cluster encompasses functional and tissue specificity that direct furanocoumarin and pyranocoumarin biosynthesis in citrus

Furanocoumarins (FCs) are plant defence compounds derived from the phenylpropanoid pathway via the coumarin umbelliferone that harbour some therapeutic benefits yet are the underlying cause of 'grapefruit-drug interactions' in humans. Most of the pathway genes have not been identified in citrus. We employed a genetic/Omics approach on citrus ancestral species and F1 populations of mandarin × grapefruit and mandarin × pummelo. Enzyme specificity was characterized by In vivo 2-oxoglutarate-dependent dioxygenase family (2OGD) activity assays. We identified a 2OGD multi-gene cluster involved in coumarin/FC/pyranocoumarin biosynthesis; Species lacking FCs in leaves/fruit were homozygous for a 655-base solo-LTR frame-disrupting insertion within one dual specificity C2'H/F6'H encoding 2OGD gene, demonstrating that integrity of this gene is fully correlated with the capacity to biosynthesize metabolites of the extended FC pathway in leaves/fruit. A second 2OGD is the prominent gene expressed in citrus roots, which contain a unique pattern of extended FC pathway metabolites, including the predominant pyranocoumarins. A third 2OGD gene encodes a single activity F6'H, which appears to be induced at the transcript level by citrus pathogens. The results provide insights into the genetic basis underlying the difference between citrus fruit FC producers (grapefruit and pummelo) and nonproducers (mandarin and orange) and provide a gene target to breed for FC-free varieties by marker-assisted breeding or genome editing.

Homospermidine synthase evolution and the origin(s) of pyrrolizidine alkaloids in Apocynaceae

PREMISE

Enzymes that are encoded by paralogous genes and produce identical specialized metabolites in distantly related plant lineages are strong evidence of parallel phenotypic evolution. Inference of phenotypic homology for metabolites produced by orthologous genes is less straightforward, since orthologs may be recruited in parallel into novel pathways. In prior research on pyrrolizidine alkaloids (PAs), specialized metabolites of Apocynaceae, the evolution of homospermidine synthase (HSS), an enzyme of PA biosynthesis, was reconstructed and a single origin of PAs inferred because HSS enzymes of all known PA-producing Apocynaceae species are orthologous and descended from an ancestral enzyme with the motif (VXXXD) of an optimized HSS.

METHODS

We increased sampling, tested the effect of amino acid motif on HSS function, revisited motif evolution, and tested for selection to infer evolution of HSS function and its correlation with phenotype.

RESULTS

Some evidence supports a single origin of PAs: an IXXXD HSS-like gene, similar in function to VXXXD HSS, evolved in the shared ancestor of all PA-producing species; loss of HSS function occurred multiple times via pseudogenization and perhaps via evolution of an IXXXN motif. Other evidence indicates multiple origins: the VXXXD motif, highly correlated with the PA phenotype, evolved two or four times independently; the ancestral IXXXD gene was not under positive selection, while some VXXXD genes were; and substitutions at sites experiencing positive selection occurred on multiple branches in the HSS-like gene tree.

CONCLUSIONS

The complexity of the genotype-function-phenotype map confounds the inference of PA homology from HSS-like gene evolution in Apocynaceae.

Phylogenomic analysis reveals exceptions to the co-evolution of ZAR1 and ZRK immune gene families in plants

BACKGROUND

HOPZ-ACTIVATED RESISTANCE 1 (ZAR1) is a nucleotide-binding leucine-rich repeat (NLR) protein functioning as a recognition hub to initiate effector-triggered immunity against bacterial pathogens. To initiate defense, ZAR1 associates with different HOPZ-ETI-DEFICIENT 1 (ZED1)-Related Kinases (ZRKs) to form resistosomes to indirectly perceive effector-induced perturbations. Few studies have focused on the phylogenomic characteristics of ZAR1 and ZRK immune gene families and their evolutionary relationships. To trace the origin and divergence of ZAR1 and ZRK immune gene families across the plant kingdom, we performed phylogenomic analyses using an extended set of plant genomes.

RESULTS

Genome-wide identification of ZAR1 and ZRK immune gene families by blast similarity searches combined with phylogenetic analysis showed that these two gene families have experienced frequent gene losses in massive lineages. Gene distribution patterns across the plant kingdom revealed that ZAR1 and ZRK emerged after the divergence of most angiosperms from Amborella and before the split of magnoliids, monocots, and eudicots. Co-occurrence of ZAR1-A and ZRKs was found in various plant species belonging to different angiosperm orders, but both genes were found to be absent in chlorophyta, bryophytes, lycophytes, ferns, and gymnosperms. We also detected a large number of concerted gene losses in angiosperms, especially within the orders Fabales, Cucurbitales, Asterales, and Apiales. All analysed monocot genomes thus far examined, except for the aroid Colocasia esculenta, were previously reported to lack both ZAR1-A and ZRKs. Here we now report other exceptions on the concerted ZAR1-A-ZRKs presence-absence pattern within several early diverging monocot lineages, including the genome of Acorus tatarinowii-a species representing the first branching monocot lineage. We also revealed strong variation in ZAR1-A-ZRKs co-occurrence within the asterid order Ericales, suggesting patterns of de-coevolution in angiosperms. Our research further shows that both gene families experienced significant diversification through various duplication events. Additionally, their evolutionary paths have been shaped by frequent gene losses and lineage-specific transposition.

CONCLUSION

This study provides novel findings on the evolution of ZAR1 and ZRK immune gene families across a wide range of plant species, suggesting that more potential exceptions can be expected when expanding the list of sequenced genomes from distinct orders. Our results provide new hypotheses about the origin and diversification of these critical immune genes for future functional studies.

Genome-Wide Study of Plant-Specific PLATZ Transcription Factors and Functional Analysis of OsPLATZ1 in Regulating Caryopsis Development of Rice (Oryza sativa L.)

Plant A/T-rich sequence- and zinc-binding protein (PLATZ) is a type of plant-specific zinc-dependent DNA-binding protein that binds to A/T-rich DNA sequences. This family is essential for plant growth, development, and stress response. In this study, 15 OsPLATZs were identified in the rice genome with complete PLATZ-conserved domains by CD-search, similar to those found in angiosperms. Multi-species phylogenetic analysis showed that PLATZs were conserved in photosynthetic organisms, and an evolutionary branch unique to angiosperms was identified among members of the PLATZ family. Fifteen OsPLATZs were represented by five groups, each with distinct characteristics. An analysis of protein structures and sequence motifs showed that OsPLATZs were similar within groups, but varied between them. The expression profile and qRT-PCR results showed that OsPLATZs had distinct expression patterns in different tissues, with some responding to stress induction. Most of the OsPLATZs localized to the nuclei, and were predicted to bind to DNA sequences by AlphaFold3, suggesting that they likely function as conventional transcription factors. We also identified OsPLATZ1, a caryopsis-specific gene that regulates grain filling and caryopsis development in rice. This research lays the foundation for exploring the structural diversity, evolutionary traits, expression profile, and possible roles of PLATZ transcription factors in rice.

Expression divergence of BAG gene family in maize under heat stress

Heat stress poses a significant challenge for maize production, especially during the spring when high temperatures disrupt cellular processes, impeding plant growth and development. The B-cell lymphoma-2 (Bcl-2) associated athanogene (BAG) gene family is known to be relatively conserved across various species. It plays a crucial role as molecular chaperone cofactors that are responsible for programmed cell death and tumorigenesis. Once the plant is under heat stress, the BAG genes act as co-chaperones and modulate the molecular functions of HSP70/HSC70 saving the plant from the damage of high temperature stress. The study was planned to identify and characterize the BAG genes for heat stress responsiveness in maize. Twenty-one (21) BAG genes were identified in the latest maize genome. The evolutionary relationship of Zea mays BAGs (ZmBAGs) with Arabidopsis thaliana, Solanum lycopersicum, Theobroma cacao, Sorghum bicolor, Ananas comosus, Physcomitrium patens, Oryza sativa and Populus trichocarpa were represented by the phylogenetic analysis. Differential expressions of BAG gene family in leaf, endosperm, anther, silk, seed and developing embryo depict their contribution to the growth and development. The in-silico gene expression analysis indicated ZmBAG-8 (Zm00001eb170080), and ZmBAG-11 (Zm00001eb237960) showed higher expression under abiotic stresses (cold, heat and salinity). The RT-qPCR further confirmed the expression of ZmBAG-8 and ZmBAG-11 in plant leaf tissue across the contrasting inbred lines and their F1 hybrid (DR-139, UML-1 and DR-139 × UML-1) when exposed to heat stress. Furthermore, the protein-protein interaction networks of ZmBAG-8 and ZmBAG-11 further elucidated their role in stress tolerance related pathways. This research offers a roadmap to plan functional research and utilize ZmBAG genes to enhance heat tolerance in grasses.

Multiomic analysis of genes related to oil traits in legumes provide insights into lipid metabolism and oil richness in soybean

Soybean (Glycine max) and common bean (Phaseolus vulgaris) diverged approximately 19 million years ago. While these species share a whole-genome duplication (WGD), the Glycine lineage experienced a second, independent WGD. Despite the significance of these WGDs, their impact on gene families related to oil-traits remains poorly understood. Here, we report an in-depth investigation of oil-related gene families in soybean, common bean, and twenty-eight other legume species. We adopted a systematic approach that included 605 RNAseq samples for transcriptome and co-expression analyses, identification of orthologous groups, gene duplication modes and evolutionary rates, and family expansions and contractions. We curated a list of oil candidate genes and found that 91.5% of the families containing these genes expanded in soybean in comparison to common bean. Notably, we observed an expansion of triacylglycerol (TAG) biosynthesis (∼3:1) and an erosion of TAG degradation (∼1.4:1) families in soybean in comparison to common bean. In addition, TAG degradation genes were two-fold more expressed in common bean than in soybean, suggesting that oil degradation is also important for the sharply contrasting seed oil contents in these species. We found 17 transcription factor hub genes that are likely regulators of lipid metabolism. Finally, we inferred expanded and contracted families and correlated these patterns with oil content found in different legume species. In summary, our results do not only shed light on the evolution of oil metabolism genes in soybean, but also present multifactorial evidence supporting the prioritization of promising candidate genes that, if experimentally validated, could accelerate the development of high-oil soybean varieties.

Identification of the MAP4K gene family reveals GhMAP4K13 regulates drought and salt stress tolerance in cotton

Mitogen-activated protein kinase kinase kinase kinases (MAP4Ks) are a class of highly conserved serine/threonine-protein kinases in eukaryotes. They participate in the typical MAPK cascade system and various signal transduction pathways regulating biological processes in plants, during stressful conditions. To date, genome-wide identification of MAP4Ks in cotton has not been reported. In this study, 77 MAP4K genes were identified in four Gossypium species. Protein characteristics, gene structures, conserved motifs and gene expression analysis were carried out. Genome-wide or fragment duplication has played an important role in the expansion of the GhMAP4K. Promoter cis-acting elements and expression patterns indicated that GhMAP4Ks are related to plant hormones (ABA, MeJA, GA, IAA, SA) and various stresses (drought, hypothermia and wound). Overexpressing GhMAP4K13 in Arabidopsis showed higher stem length in response to drought and salt stress. The wilting degree in virus-induced GhMAP4K13 gene silenced plants was substantially greater than wild type plants under drought and salt stress. Transcriptomic analysis showed that most differentially expressed genes were involved in the MAPK signaling pathway, carbon metabolism and porphyrin metabolism. Additionally, transgenic Arabidopsis and VIGS cotton showed that GhMAP4K13 was positively responsive to drought and salt stresses. This study will play an important role in understanding the function of the MAP4K gene family in response to abiotic stress in cotton.

Plastid-nuclear coevolution of ribosomal protein genes in papilionoid legumes

In plants, cellular function is orchestrated by three distinct genomes located within the nucleus, mitochondrion, and plastid. These genomes are interdependent, requiring tightly coordinated maintenance and expression. Plastids host several multisubunit protein complexes encoded by both the plastid and nuclear genomes. To investigate plastid-nuclear coevolution, this study focused on plastid ribosomal protein genes that are encoded by both plastid and nuclear genomes from 50 taxa across 15 of the 22 early branching major clades of the legume subfamily Papilionoideae. Comparative analysis of substitution rates was conducted across five gene sets: nuclear-encoded plastid-targeted ribosomal protein genes (NuCpRP), nuclear-encoded cytosol-targeted ribosomal genes (NuCyRP), other nuclear-encoded plastid-targeted genes that are not involved in ribosomes (NuCpOT), plastid-encoded ribosomal protein genes (CpRP) and plastid-encoded photosynthesis genes (CpPS).1 Elevated nonsynonymous substitution rates (dN) and ratios of nonsynonymous to synonymous substitution rates (dN/dS; ω) were observed in both CpRP and NuCpRP compared to the other gene sets. Significant differences in dN for CpRP and NuCpRP were found between the papilionoid 50-kb inversion clade and other legumes. Using coevolution statistics and evolutionary rate covariation, strong signals of cytonuclear coevolution were identified, where nonsynonymous substitutions in CpRP and NuCpRP genes co-occur along the same branches of the Papilionoideae phylogeny. Increased ω in a few CpRP genes was due to intensified positive selection whereas most of the CpRP and NuCpRP increased ω was caused by relaxed purifying selection. This pattern not only underscores the role of cytonuclear incompatibility in driving speciation but also highlights its constraints on the genetic enhancement of papilionoid crop species.

Genome-wide identification, classification, and expression profiling of LAC gene family in sesame

BACKGROUND

Laccases (LACs) are vital plant growth and development enzymes, participating in lignin biopolymerization and responding to stress. However, the role of LAC genes in plant development as well as stress tolerance, is still not well understood, particularly in sesame (Sesamum indicum L.), an important oilseed crop.

RESULTS

In this study, 51 sesame LAC genes (SiLACs) were identified, which were unevenly distributed across different chromosomes. The phylogeny of Arabidopsis LAC (AtLACs) subdivided the SiLAC proteins into seven subgroups (Groups I-VII), of which Group VII contained only sesame LACs. Within the same subgroup, SiLACs exhibit comparable structures and conserved motifs. The promoter region of SiLACs harbors various cis-acting elements that are related to plant growth, phytohormones, and stress responses. Most SiLACs were expressed in the roots and stems, whereas some were expressed specifically in flowers or seeds. RNA-seq analysis revealed that 19 SiLACs exhibited down-regulation and three showed up-regulation in response to drought stress, while 15 SiLACs were down-regulated and four up-regulated under salt stress. Additionally, qRT-PCR analysis showcased that certain SiLAC expression was significantly upregulated as a result of osmotic and salt stress. SiLAC5 and SiLAC17 exhibited the most significant changes in expression under osmotic and salt stresses, indicating that they may serve as potential targets for improving sesame resistance to various stresses.

CONCLUSIONS

Our study offers a thorough comprehension of LAC gene structure, classification, evolution, and abiotic stress response in sesame plants. Furthermore, we provide indispensable genetic resources for sesame functional characterization to enhance its tolerance to various abiotic stresses.

Plant Nuclear Factor Y (NF-Y) Transcription Factors: Evolving Insights into Biological Functions and Gene Expansion

Gene expansion is a common phenomenon in plant transcription factor families; however, the underlying molecular mechanisms remain elusive. Examples of gene expansion in transcription factors are found in all eukaryotes. One example is plant nuclear factor Y (NF-Y) transcription factors. NF-Y is ubiquitous to eukaryotes and comprises three independent protein families: NF-YA, NF-YB, and NF-YC. While animals and fungi mostly have one of each NF-Y subunit, NF-Y is greatly expanded in plants. For example, humans have one each of NF-YA, NF-YB, and NF-YC, while the model plant Arabidopsis has ten each of NF-YA, NF-YB, and NF-YC. Our understanding of the plant NF-Y, including its biological roles, molecular mechanisms, and gene expansion, has improved over the past few years. Here we will review its biological roles and focus on studies demonstrating that NF-Y can serve as a model for plant gene expansion. These studies show that NF-Y can be classified into ancestrally related subclasses. Further, the primary structure of each NF-Y contains a conserved core domain flanked by non-conserved N- and C-termini. The non-conserved N- and C-termini, under pressure for diversifying selection, may provide clues to this gene family's retention and functional diversification following gene duplication. In summary, this review demonstrates that NF-Y expansion has the potential to be used as a model to study the gene expansion and retention of transcription factor families.

Genome-Wide Identification and Expression Analysis of NAC Gene Family Members in Seashore Paspalum Under Salt Stress

The NAC gene family plays a crucial role in plant growth, development, and responses to biotic and abiotic stresses. Paspalum Vaginatum, a warm-season turfgrass with exceptional salt tolerance, can be irrigated with seawater. However, the NAC gene family in seashore paspalum remains poorly understood. In this study, genome-wide screening and identification were conducted based on the NAC (NAM) domain hidden Markov model in seashore paspalum, resulting in the identification of 168 PvNAC genes. A phylogenetic tree was constructed, and the genes were classified into 18 groups according to their topological structure. The physicochemical properties of the PvNAC gene family proteins, their conserved motifs and structural domains, cis-acting elements, intraspecific collinearity analysis, GO annotation analysis, and protein-protein interaction networks were analyzed. The results indicated that the majority of PvNAC proteins are hydrophilic and predominantly localized in the nucleus. The promoter regions of PvNACs are primarily enriched with light-responsive elements, ABRE motifs, MYB motifs, and others. Intraspecific collinearity analysis suggests that PvNACs may have experienced a large-scale gene duplication event. GO annotation indicated that PvNAC genes were essential for transcriptional regulation, organ development, and responses to environmental stimuli. Furthermore, the protein interaction network predicted that PvNAC73 interacts with proteins such as BZIP8 and DREB2A to form a major regulatory hub. The transcriptomic analysis investigates the expression patterns of NAC genes in both leaves and roots under varying durations of salt stress. The expression levels of 8 PvNACs in roots and leaves under salt stress were examined and increased to varying degrees under salt stress. The qRT-PCR results demonstrated that the expression levels of the selected genes were consistent with the FPKM value trends observed in the RNA-seq data. This study established a theoretical basis for understanding the molecular functions and regulatory mechanisms of the NAC gene family in seashore paspalum under salt stress.

Genome-Wide Characterization and Analysis of the bHLH Gene Family in Perilla frutescens

Perilla frutescens (L.) Britt. is a traditional medicinal and culinary plant with a long history of cultivation and significant potential for broader utilization. The basic helix-loop-helix (bHLH) gene family is essential for regulating plant growth, development, stress responses, and secondary metabolism. However, the bHLH gene family in P. frutescens has not yet been characterized. In this study, a total of 205 bHLH genes were identified in P. frutescens through genome mining and analysis. Phylogenetic analysis classified these PfbHLH genes into 23 distinct subfamilies. Promoter analysis revealed an enrichment of cis-acting elements linked to plant hormone signaling and stress responses, suggesting their potential regulatory roles in development, growth, and stress adaptation. Expression profiling based on publicly available RNA-seq data demonstrated tissue-specific expression patterns of PfbHLH genes in roots, stems, and leaves. Four PfbHLH genes (PfbHLH66, PfbHLH45, PfbHLH13, and PfbHLH5) showed significant responses to methyl jasmonate (MeJA) induction. Yeast one-hybrid assays confirmed that these PfbHLH proteins could bind to the cis-acting G-box (CACGTG) element. This study offers new perspectives on the evolution, regulatory mechanisms, and functional roles of the bHLH gene family in P. frutescens. The findings deepen our understanding of the functional diversity within this gene family and establish a foundation for genetic enhancement and the biosynthesis of medicinal compounds in the species.

Multi-omics analysis reveals the evolution, function, and regulatory mechanisms of SPF pheromones in Anurans

Pheromones play a pivotal role in chemical communication across various taxa, with protein-based pheromones being particularly significant in amphibian courtship and reproduction. In this study, we investigate the Emei music frog (Nidirana daunchina), which utilizes both acoustic and chemical signals for communication. Base on a de novo assembled genome of a male Emei music frog, we identify substantial expansion in four pheromone-related gene families associated with chemical communication. Notably, six members of the two-domain three-finger protein (2D-TFP) family, belonging to the sodefrin precursor-like factor (SPF) pheromone system, exhibited high and specific expression in the male post-axillary glands during the breeding season. Structural and evolutionary analyses confirm the presence of the SPF system across amphibians, classifiable into four distinct classes (two within urodeles and two within anurans). We propose a complete regulatory network governing SPF secretion via the hypothalamic-pituitary-testicular-breeding gland axis, and suggest testosterone synthesis as the pivotal pathway. Behavioral experiments further reveal a previously unknown female-attractant role of SPF in anurans. Overall, these findings not only highlight the underestimated diversity and function of pheromones in anurans, but also provide important insights into the evolution of protein-based pheromones in vertebrates.

Evolutionary analysis of anthocyanin biosynthetic genes: insights into abiotic stress adaptation

Anthocyanin regulation can be fruitfully explored from a diverse perspective by studying distantly related model organisms. Land plants pioneers faced a huge evolutionary leap, involving substantial physiological and genetic changes. Anthocyanins have evolved alongside these changes, becoming versatile compounds capable of mitigating terrestrial challenges such as drought, salinity, extreme temperatures and high radiation. With the accessibility of whole-genome sequences from ancient plant lineages, deeper insights into the evolution of key metabolic pathways like phenylpropanoids have emerged. Despite understanding the function of anthocyanins under stress, gaps remain in uncovering the precise metabolic and regulatory mechanisms driving their overproduction under stressful conditions. For example, the regulatory effect of reactive oxygen species (ROS) on well-known transcription factors like MYBs is not fully elucidated. This manuscript presents an evolutionary analysis of the anthocyanin biosynthetic pathway to elucidate key genes. CINNAMATE 4-HYDROXYLASE (C4H) and CHALCONE ISOMERASE (CHI2) received particular attention. C4H exposes remarkable differences between aquatic and land plants, while CHI2 demonstrates substantial variation in gene copy number and sequence similarity across species. The role of transcription factors, such as MYB, and the involvement of ROS in the regulation of anthocyanin biosynthesis are discussed. Complementary gene expression analyses under abiotic stress in Arabidopsis thaliana, Selaginella moellendorffii, and Marchantia polymorpha reveal intriguing gene-stress relationships. This study highlights evolutionary trends and the regulatory complexity of anthocyanin production under abiotic stress, providing insights and opening avenues for future research.

Genome-wide identification of the WD40 protein family and functional characterization of AaTTG1 in Artemisia annua

Sweet wormwood (Artemisia annua), an annual herb belonging to the Compositae family, is the main source of the potent anti-malarial drug artemisinin, which is mainly produced in glandular trichomes of A. annua leaves. The WD40 protein family is one of the largest protein families in eukaryotes and plays crucial roles in regulating plant growth and development, stress responses, and secondary metabolite biosynthesis. However, WD40 proteins have not been comprehensively identified in A. annua. In this study, we identified 236 WD40 proteins in the A. annua genome and examined their conserved domains, motifs, and cis-regulatory elements, gene structures, chromosomal distribution, duplication events of their encoding genes. Furthermore, we isolated and characterized TRANSPARENT TESTA GLABROUS 1 (AaTTG1), a homolog of Arabidopsis TTG1, and confirmed that AaTTG1 was localized to the nucleus and cytoplasm. Indeed, AaTTG1 can rescue the glabrous phenotype of the Arabidopsis ttg1 mutant and enhanced trichome production when heterologously expressed in wild-type Arabidopsis plants. Transgenic A. annua lines overexpressing AaTTG1 displayed a significantly higher density of glandular trichomes and higher artemisinin contents. Transgenic A. annua lines with inhibited AaTTG1 function had fewer glandular trichomes and lower artemisinin levels. Moreover, we demonstrated that AaTTG1 positively regulates glandular trichome development in A. annua through interactions with AaSPL9. This study thus provides fundamental insights into the role of WD40 proteins in A. annua and introduces a promising approach to enhance artemisinin production by manipulating glandular trichome development in this valuable medicinal plant.

Identification, Phylogeny, and Expression Profiling of Pineapple Heat Shock Proteins (HSP70) Under Various Abiotic Stresses

Pineapple (Ananas comosus (L.) Merr.) is an economically significant and delicious tropical fruit. Pineapple commercial production faces severe decline due to abiotic stresses, which affect the development and quality of pineapple fruit. Heat shock protein 70 (HSP70) plays an essential role in abiotic stress tolerance. However, the pineapple HSP70 family identification and expression analysis in response to abiotic stresses has not been studied. To explore the functional role of AcHSP70, different abiotic stress treatments were applied to pineapple cultivar "Bali" seedlings. A total of 21 AcHSP70 members were identified in the pineapple genome. The identified genes were classified into four subfamilies (I-IV) using phylogenetic analysis. The AcHSP70 family is expressed under different stress conditions. Quantitative real time polymerase chain reaction (qRT-PCR) revealed the expression pattern of the AcHSP70 family under cold, drought, salt, and heat stress. The expression level of genes such as AcHSP70-2 increased under heat, cold, and drought stress, while the expression level of genes such as AcHSP70-3 decreased under salt stress. Furthermore, the expression profile of AcHSP70s in different tissues and development stages was analyzed using transcriptome analysis. The HSP70 genes exhibited unique expression patterns in pineapple tissue at different developmental stages. The study therefore provides a list of HSP70 genes with substantial roles in abiotic stress response and valuable information for understanding AcHSP70 functional characteristics during abiotic stress tolerance in pineapple.

Dynamic Expressions of Yellow Stripe-Like (YSL) Genes During Pod Development Shed Light on Associations with Iron Distribution in Phaseolus vulgaris

The global prevalence of iron deficiency-induced "hidden hunger" highlights a critical health concern, underscoring the pressing need to improve iron nutrition through safe and efficient means, such as increasing iron intake from plant-based foods. Yellow Stripe-Like (YSL) genes play a crucial role in long-distance iron transport between source and sink tissues in plants. Here, we report on the analysis of YSL family genes in the common bean (Phaseolus vulgaris L.), an iron-rich legume crop. We identified 9 YSL genes in the common bean genome using BLAST and HMM methods. Gene duplication analysis revealed that PvYSL7a and PvYSL7b originated through tandem duplication events. Structural analysis noted an absence of conservative motifs in PvYSL3b and PvYSL7a, which led to distinct predicted 3D protein structures. Leveraging publicly available RNA-seq data from developing bean pods, the expression patterns of PvYSL genes alongside pod and seed development were analyzed. Notably, PvYSL7a and PvYSL7b, as well as PvYSL1a and PvYSL1b, exhibited diverged expression patterns in seeds, signifying their functional divergence in this tissue. Moreover, PvYSL3a and PvYSL3b exhibited divergent expression patterns in both pod walls and seeds during pod development, underscoring their distinct roles in facilitating iron transportation between pods and seeds. This study provides valuable insights into the gene regulatory basis of iron accumulation in bean pods and seeds.

Exposure of Arabidopsis thaliana Mutants to Genotoxic Stress Provides New Insights for the Involvement of TDP1α and TDP1β genes in DNA-Damage Response

Genotoxic stress activates the DNA-damage response (DDR) signalling cascades responsible for maintaining genome integrity. Downstream DNA repair pathways include the tyrosyl-DNA phosphodiesterase 1 (TDP1) enzyme that hydrolyses the phosphodiester bond between the tyrosine of topoisomerase I (TopI) and 3'-phosphate of DNA. The plant TDP1 subfamily contains the canonical TDP1α gene and the TDP1β gene whose functions are not fully elucidated. The current study proposes to investigate the involvement of TDP1 genes in DDR-related processes by using Arabidopsis thaliana mutants treated with genotoxic agents. The phenotypic and molecular characterization of tdp1α, tdp1β and tdp1α/β mutants treated with cisplatin (CIS), curcumin (CUR), NSC120686 (NSC), zeocin (ZEO), and camptothecin (CPT), evidenced that while tdp1β was highly sensitive to CIS and CPT, tdp1α was more sensitive to NSC. Gene expression analyses showing upregulation of the TDP2 gene in the double mutant indicate the presence of compensatory mechanisms. The downregulation of POL2A gene in the tdp1β mutant along with the upregulation of the TDP1β gene in pol2a mutants, together with its sensitivity to replication inhibitors (CIS, CTP), point towards a function of this gene in the response to replication stress. Therefore, this study brings novel information relative to the activity of TDP1 genes in plants.

Zebrafish: unraveling genetic complexity through duplicated genes

The zebrafish is an invaluable model organism for genetic, developmental, and disease research. Although its high conservation with humans is often cited as justification for its use, the zebrafish harbors oft-ignored genetic characteristics that may provide unique insights into gene structure and function. Zebrafish, along with other teleost fish, underwent an additional round of whole genome duplication after their split from tetrapods-resulting in an abundance of duplicated genes when compared to other vertebrates. These duplicated genes have evolved in distinct ways over the ensuing 350 million years. Thus, each gene within a duplicated gene pair has nuanced differences that create a unique identity. By investigating both members of the gene pair together, we can elucidate the mechanisms that underly protein structure and function and drive the complex interplay within biological systems, such as signal transduction cascades, genetic regulatory networks, and evolution of tissue and organ function. It is crucial to leverage such studies to explore these molecular dynamics, which could have far-reaching implications for both basic science and therapeutic development. Here, we will review the role of gene duplications and the existing models for gene divergence and retention following these events. We will also highlight examples within each of these models where studies comparing duplicated genes in the zebrafish have yielded key insights into protein structure, function, and regulation.

The parallel narrative of RGF/GLV/CLEL peptide signalling

Plant peptide families share distinct characteristics, and many members are in homologous signalling pathways controlling development and responses to external signals. The root meristem growth factor (RGF) peptides/GOLVEN (GLV)/CLAVATA3-ESR-related like (CLEL) are a family of short signalling peptides that are derived from a precursor protein and undergo post-translational modifications. Their role in root meristem development is well established and recent efforts have identified subtilase processing pathways and several downstream signalling components. This discovery has enabled the convergence of previously distinct pathways and enhanced our understanding of plant developmental processes. Here, we review the structure-function relationship of RGF peptides, the post-translational modification pathways, and the downstream signalling mechanisms and highlight components of these pathways that are known in non-RGF-mediated pathways.

Heat shock responsive genes in Brassicaceae: genome-wide identification, phylogeny, and evolutionary associations within and between genera

Heat stress affects the growth and development of Brassicaceae crops. Plant breeders aim to mitigate the effects of heat stress by selecting for heat stress tolerance, but the genes responsible for heat stress in Brassicaceae remain largely unknown. During heat stress, heat shock proteins (HSPs) function as molecular chaperones to aid in protein folding, and heat shock transcription factors (HSFs) serve as transcriptional regulators of HSP expression. We identified 5002 heat shock related genes, including HSPs and HSFs, across 32 genomes in Brassicaceae. Among these, 3347 genes were duplicated, with segmented duplication primarily contributing to their expansion. We identified 466 physical gene clusters, including 240 homogenous clusters and 226 heterogeneous clusters, shedding light on the organization of heat shock related genes. Notably, 37 genes were co-located with published thermotolerance quantitative trait loci, which supports their functional role in conferring heat stress tolerance. This study provides a comprehensive resource for the identification of functional Brassicaceae heat shock related genes, elucidates their clustering and duplication patterns and establishes the genomic foundation for future heat tolerance research. We hypothesise that genetic variants in HSP and HSF genes in certain species have potential for improving heat stress tolerance in Brassicaceae crops.

Genome-Wide Identification, Classification, Expression Analysis, and Screening of Drought and Heat Resistance-Related Candidates of the Rboh Gene Family in Wheat

Plant respiratory burst oxidase homologs (Rbohs) are key enzymes that produce reactive oxygen species (ROS), which serve as signaling molecules regulating plant growth and stress responses. In this study, 39 TaRboh genes (TaRboh01-TaRboh39) were identified. These genes were distributed unevenly among the wheat genome's fourteen chromosomes, with the exception of homoeologous group 2 and 7 and chromosomes 4A, as well as one unidentified linkage group (Un). TaRbohs were classified into ten distinct clades, each sharing similar motif compositions and gene structures. The promoter regions of TaRbohs contained cis-elements related to hormones, growth and development, and stresses. Furthermore, five TaRboh genes (TaRboh26, TaRboh27, TaRboh31, TaRboh32, and TaRboh34) exhibited strong evolutionary conservation. Additionally, a Ka/Ks analysis confirmed that purifying selection was the predominant force driving the evolution of these genes. Expression profiling and qPCR results further indicated differential expression patterns of TaRboh genes between heat and drought stresses. TaRboh11, TaRboh20, TaRboh22, TaRboh24, TaRboh29, and TaRboh34 were significantly upregulated under multiple stress conditions, whereas TaRboh30 was only elevated in response to drought stress. Collectively, our findings provide a systematic analysis of the wheat Rboh gene family and establish a theoretical framework for our future research on the role of Rboh genes in response to heat and drought stress.

Genome-Wide Identification and Characterization of the Laccase Gene Family in Fragaria vesca and Its Potential Roles in Response to Salt and Drought Stresses

Laccase (LAC, EC 1.10.3.2) is integral to the formation of lignin synthesis, flavonoid production, and responses to both biotic and abiotic stresses. While recent studies have characterized numerous LAC gene families and their functions across various plants, information regarding LAC genes in woodland strawberry (Fragaria vesca) remains limited. In this study, we identified a total of 57 FvLAC genes in the Fragaria vesca genome, which were phylogenetically categorized into five distinct groups. Analysis of the gene structures revealed a uniformity in the exon-intron structure among the subgroups, while conserved motifs identified unique motifs specific to certain subgroups, suggesting functional variations. Chromosomal localization studies indicated that FvLACs are distributed across seven chromosomes, and collinearity analysis demonstrated that FvLACs exhibit collinearity within the species. Additionally, cis-acting element analysis suggested that FvLAC genes are involved in stress responses, hormone responses, light responses, and the growth and development of plants. qRT-PCR demonstrated that FvLACs responded to salt, drought, and hormone stresses, with the expression levels of FvLAC24, FvLAC32, and FvLAC51 continuously increasing under these stress conditions. Furthermore, transgenic yeast experiments revealed that FvLAC51 enhanced yeast tolerance to both salt and drought stresses, while FvLAC24 and FvLAC32 negatively regulated yeast tolerance under these same conditions. These findings provide a theoretical foundation for further investigation into the functions of FvLAC genes in woodland strawberry.

Regulatory Genes in Eyespot Formation and Function of Mytilus coruscus

Light sensitivity is important for marine benthic invertebrates, and it plays a vital role in the marine bivalves settling. Animal visual systems are enormously diverse; their development appears to be controlled by a set of conserved retinal determination genes (RDGs). Eyespots, as the simplest animal eyes, their appearance indicates the important effect on mussel larvae attachment. Nevertheless, the molecular mechanism of the eyespot's development in Mytilus coruscus larvae is not clear. In this study, we identified 11 genes which play a regulatory role in the visual system (i.e. Pax1/9, Pax2/5/8, Pax6, Pax3/7, Six1/2, Six3/6, Six4/5, Dach, Eya, Brn and Tbx2) from transcriptome data and the whole genome sequence of M. coruscus. The results of chromosome localization showed that 11 genes were distributed on different chromosomes. Subcellular mapping revealed that all the proteins except Brn were located in the nucleus. Phylogeny and gene structure analyses revealed that the Pax members were divided into four subfamilies, the Six members were divided into three subfamilies and structures within the same subfamily were relatively conserved. Quantitative real-time PCR (qPCR) showed that Dach, Pax6, Pax3/7, Six1/2 and Six4/5 were expressed at high levels during the pediveliger stage. Moreover, Six1/2 and Six4/5 were highly expressed in mantle tissues. Subsequent overall in situ hybridization experiments in the planktonic larval stage revealed that Pax6, Six1/2 and Six4/5 detected signals in the region of the eyespot. Based on these analyses, we suggested that the development of vision in M. coruscus not only depended on the expression pattern of Pax6, but perhaps also related to Six1/2 and Six4/5 in the planktonic larval stage, while Six1/2 and Six4/5 were the dominant genes for visual function in the adult mussel. This study made a comprehensive analysis of the visual function of M. coruscus at the genome level, which helps us to understand the intrinsic mechanism of the visual system of marine bivalves, and also provides a molecular basis for improving the attachment and metamorphosis rate of M. coruscus larvae.

Identification and analysis of drought-responsive F-box genes in upland rice and involvement of OsFBX148 in ABA response and ROS accumulation

BACKGROUND

Upland rice varieties exhibit significant genetic diversity and broad environmental adaptability, making them ideal candidates for identifying consistently expressed stress-responsive genes. F-box proteins typically function as part of the SKP1-CUL1-F-box protein (SCF) ubiquitin ligase complexes to precisely regulate gene expression and protein level, playing essential roles in the modulation of abiotic stress responses. Therefore, utilizing upland rice varieties for screening stress-responsive F-box genes is a highly advantageous approach.

RESULTS

Through mRNA-seq analysis in the Brazilian upland rice (cv. IAPAR9), the research identified 29 drought-responsive F-box genes. Gene distribution and duplication analysis revealed these genes are distributed on 11 of the 12 chromosomes and 10 collinear gene pairs were identified on different chromosomes. 13 cis-elements or binding sites were identified in the promoters of the 29 drought-responsive F-box genes by analysis. Protein domain, stability and subcellular localization analysis results suggest that these F-box proteins possess F-box domain and several other domains, and they are mostly unstable proteins with subcellular localization in cytoplasm, nucleus, chloroplasts, mitochondria and endoplasmic reticulum. Most of drought-responsive F-box genes exhibited expression in various tissues such as root, stem, leaf, leaf sheath and panicle except for OsFBO10 and OsFBX283. These genes exhibited various responses to abiotic stresses such as osmotic, cold, heat, and salt stresses, along with ABA treatment. Importantly, a frame-shift mutation in OsFBX148 was created in the ZH11 variety, leading to altered ABA signal transduction and ROS accumulation. The study further elucidated the interaction of OsFBX148 with SKP1 family proteins OSK4/7/17 to form the SCF complex, dependent on the F-box domain.

CONCLUSIONS

The research identified and analyzed 29 drought-responsive F-box genes in upland rice and provides valuable insights into the role of OsFBX148 in ABA and ROS responses. It establishes a basis for future exploration of F-box genes in improving resistance to abiotic stresses, especially drought.

Bioinformatics and Expression Analyses of the TaATLa Gene Subfamily in Wheat (Triticum aestivum L.)

Amino acids are the main form of nitrogen in plants, and their transport across cell membranes relies on amino acid transporters (AATs). Among the plant AATs, the TaATLa subfamily comprises 18 members, yet the bioinformatics characteristics and functions of TaATLa genes in common wheat remain poorly understood due to their complex genomes. This study performed genomic analyses of TaATLas. These analyses included chromosome distributions, evolutionary relationships, collinearity, gene structures, and expression patterns. An analysis of cis-acting elements and predicted miRNA-TaATLas regulatory networks suggests that TaATLas are regulated by light, hormones, and stress signals. Functional assays revealed that TaATLa6 transports glutamine (Gln), glutamate (Glu), and aspartate (Asp) in yeast. In contrast, TaATLa4 specifically transports Gln and Asp. Furthermore, TaATLas exhibits diverse gene expression patterns, with TaATLa4-7D enhancing yeast heat tolerance in a heterologous expression system, indicating its potential role in adapting to environmental stress by regulating amino acid transport and distribution. This study sheds light on the functional roles of TaATLa genes, with implications for improving nitrogen use in wheat and other crop species.

Genomic survey and evolution analysis of calcium-dependent protein kinases in plants and their stress-responsive patterns in populus

BACKGROUND

Calcium-dependent protein kinases (CDPKs) phosphorylate downstream target proteins in response to signals transmitted by free calcium ions (Ca2+, one of the second messengers) and thus play important regulatory roles in many biological processes, such as plant growth, development, and stress response.

RESULTS

A bioinformatic analysis, as well as thorough evolutionary and expression investigations, were conducted to confirm previous reports of functional evidence for plant CDPKs. Using the Phytozome database's BLAST search engine and the HMM search tool in TBtools software, we discovered that CDPKs are well conserved from green algae to flowering angiosperms in various gene family sizes. Additional investigations of the obtained CDPKs revealed high conservation of domain and motif numbers, gene architectures, and patterns. However, this conservation differed among plant species. Phylogenetic analysis demonstrated that the CDPK gene family diverged from a common ancient gene. Similarly, investigations into plant interspecies evolutionary relationships revealed common ancestral plant species, suggesting speciation of plants and evolution based on plant adaptation and diversification. A search for the driving force of CDPK gene family expansion revealed that dispersed duplication events, among other duplication events, contributed largely to CDPK gene family expansion. Gene localization analysis in P. trichocarpa  demonstrated that most CDPK genes are localized within several cell organelles and bind other kinases and proteins to perform their biological functions efficiently. Using RNA-seq data and qPCR analyses, we postulated that PtCDPKs play functional roles in abiotic stress responses by regulating cold, heat, drought and salt stress to varying extents.

CONCLUSION

The CDPK genes are well conserved in plants and are critical entities in abiotic stress regulation, and further exploration and manipulation of these genes in the future may provide solutions to some of the challenges in agriculture, forestry and food security.

Phylogenomic and synteny analysis of BAHD and SCP/SCPL gene families reveal their evolutionary histories in plant specialized metabolism

Plant chemical diversity is largely owing to a number of enzymes which catalyse reactions involved in the assembly, and in the subsequent chemical modifications, of the core structures of major classes of plant specialized metabolites. One such reaction is acylation. With this in mind, to study the deep evolutionary history of BAHD and the serine-carboxypeptidase-like (SCPL) acyltransferase genes, we assembled phylogenomic synteny networks based on a large-scale inference analysis of orthologues across whole-genome sequences of 126 species spanning Stramenopiles and Archaeplastida, including Arabidopsis thaliana, tomato (Solanum lycopersicum) and maize (Zea mays). As such, this study combined the study of genomic location with changes in gene sequences. Our analyses revealed that serine-carboxypeptidase (SCP)/serine-carboxypeptidase-like (SCPL) genes had a deeper evolutionary origin than BAHD genes, which expanded massively on the transition to land and with the development of the vascular system. The two gene families additionally display quite distinct patterns of copy number variation across phylogenies as well as differences in cross-phylogenetic syntenic network components. In unlocking the above observations, our analyses demonstrate the possibilities afforded by modern phylogenomic (syntenic) networks, but also highlight their current limitations, as demonstrated by the inability of phylogenetic methods to separate authentic SCPL acyltransferases from standard SCP peptide hydrolases.This article is part of the theme issue 'The evolution of plant metabolism'.

Functional Divergence of the Closely Related Genes PhARF5 and PhARF19a in Petunia hybrida Flower Formation and Hormone Signaling

The ARF gene family plays a vital role in regulating multiple aspects of plant growth and development. However, detailed research on the role of the ARF family in regulating flower development in petunia and other plants remains limited. This study investigates the distinct roles of PhARF5 and PhARF19a in Petunia hybrida flower development. Phylogenetic analysis identified 29 PhARFs, which were grouped into four clades. VIGS-mediated silencing of PhARF5 and PhARF19a led to notable phenotypic changes, highlighting their non-redundant functions. PhARF5 silencing resulted in reduced petal number and limb abnormalities, while PhARF19a silencing disrupted corolla tube formation and orientation. Both genes showed high expression in the roots, leaves, and corollas, with nuclear localization. The transcriptomic analysis revealed significant overlaps in DEGs between PhARF5 and PhARF19a silencing, indicating shared pathways in hormone metabolism, signal transduction, and stress responses. Phytohormone analysis confirmed their broad impact on phytohormone biosynthesis, suggesting involvement in complex feedback mechanisms. Silencing PhARF5 and PhARF19a led to differential transcription of numerous genes related to hormone signaling pathways beyond auxin signaling, indicating their direct or indirect crosstalk with other phytohormones. However, significant differences in the regulation of these signaling pathways were observed between PhARF5 and PhARF19a. These findings reveal the roles of ARF genes in regulating petunia flower development, as well as the phylogenetic distribution of the PhARFs involved in this process. This study provides a valuable reference for molecular breeding aimed at improving floral traits in the petunia genus and related species.

Plant pattern recognition receptors: from evolutionary insight to engineering

The plant immune system relies on germline-encoded pattern recognition receptors (PRRs) that sense foreign and plant-derived molecular patterns, and signal health threats. Genomic and pangenomic data sets provide valuable insights into the evolution of PRRs and their molecular triggers, which is furthering our understanding of plant-pathogen co-evolution and convergent evolution. Moreover, in silico and in vivo methods of PRR identification have accelerated the characterization of receptor-ligand complexes, and advances in protein structure prediction algorithms are revealing novel PRR sensor functions. Harnessing these recent advances to engineer PRRs presents an opportunity to enhance plant disease resistance against a broad spectrum of pathogens, enabling more sustainable agricultural practices. This Review summarizes both established and innovative approaches to leverage genomic data and translate resulting evolutionary insights into engineering PRR recognition specificities.

Evolutionary dynamics and functional characterization of proximal duplicated sorbitol-6-phosphate dehydrogenase genes in Rosaceae

Sorbitol is a critical photosynthate and storage substance in the Rosaceae family. Sorbitol 6-phosphate dehydrogenase (S6PDH) functions as the pivotal rate-limiting enzyme in sorbitol synthesis. The origin and functional diversification of S6PDH in Rosaceae remain unclear, largely due to the complicated interplay of gene duplications. Here, we investigated the synteny relationships among all identified S6PDH genes in representative genomes within the Rosaceae family. By integrating phylogenetic analyses, we elucidated the lineage-specific expansion and syntenic conservation of S6PDH across diverse Rosaceae plant lineages. We found that S6PDH can be traced back to a pair of proximal duplicated genes of the common ancestor of the Rosaceae, and the further amplification of S6PDH in the Maleae primarily relies on WGD events in their lineages. In Rosaceae species, multiple copies of the S6PDH gene are preliminarily divided into two main clades (Clade 1 and Clade 2) based on sequence similarity. These clades have evolved to acquire different functional directions. In Clade 1, lineage-specific transposition events in the Amygdaloideae have led to changes in gene expression patterns and promoted lineage evolution. This is mainly characterized by a decrease in enzymatic activity and transcriptional expression in the leaves, but also includes specific functional diversification, such as sustained post-harvest fruit expression and enhanced expression under biotic stress in certain tissues. In contrast, S6PDH in the Rosoideae and Dryadoideae has not undergone additional duplications beyond early proximal duplication. The loss of exons and variations in exon length might the key factor leading to reduced enzymatic activity in the Clade 2 proximal gene pairs. Collectively, our findings illuminate the dynamic nature of S6PDH evolution and reveal the intricate interplay between duplication, transposition, and functional diversification. This work not only contributes valuable insights into the genetic mechanisms underlying sorbitol metabolism but also establish a crucial foundation for future investigations aimed at comprehensively characterizing the variations of sorbitol metabolism across different subfamilies within the Rosaceae family.

Origin, Evolution, and Diversification of the Expansin Family in Plants

The cell wall is a crucial feature that allows ancestral streptophyte green algae to colonize land. Expansin, an extracellular protein that mediates cell wall loosening in a pH-dependent manner, could be a powerful tool for studying cell wall evolution. However, the evolutionary trajectory of the expansin family remains largely unknown. Here, we conducted a comprehensive identification of 2461 expansins across 64 sequenced species, ranging from aquatic algae to terrestrial plants. Expansins originated in chlorophyte algae and may have conferred the ability to loosen cell walls. The four expansin subfamilies originated independently: α-expansin appeared first, followed by β-expansin, and then expansin-like A and expansin-like B, reflecting the evolutionary complexity of plant expansins. Whole genome duplication/segmental duplication and tandem duplication events greatly contributed to expanding the expansin family. Despite notable changes in sequence characteristics, the intron distribution pattern remained relatively conserved among different subfamilies. Phylogenetic analysis divided all the expansins into five clades, with genes from the same subfamily tending to cluster together. Transcriptome data from 16 species across ten lineages and qRT-PCR analysis revealed varying expression patterns of expansin genes, suggesting functional conservation and diversification during evolution. This study enhances our understanding of the evolutionary conservation and dynamics of the expansin family in plants, providing insight into their roles as cell wall-loosening factors.

Genome-wide characterization of PEBP genes in Mung bean (Vigna radiata L.) with functional analysis of VrFT1 in relation to photoperiod

Mung bean (Vigna radiata L.), a widely cultivated legume, belongs to the Fabaceae family's Papilionoideae subfamily. Although Phosphatidylethanolamine-binding protein (PEBP) genes have been identified in several plant species, their presence and function in mung bean remain largely unexplored. In this study, we identified seven VrPEBP genes from mung bean and classified them into four clades: FT, MFT, TFL and FT-like. Cis-regulatory element analysis revealed that VrPEBP genes may play a role in light, hormone, and stress responses. Quantitative real-time PCR (qRT-PCR) analysis indicated that VrPEBPs were constitutively expressed in various tissues. However, tissue-specific expression patterns were observed among VrPEBP genes. Under short-day (SD) conditions, VrFT1 and VrMFT1 exhibited significantly higher expression levels than under long-day (LD) conditions at 8 and 4 h, respectively. Conversely, VrTFL2 and VrTFL3 showed significantly higher expression levels under LD conditions compared to SD conditions at 8 and 12 h, respectively. The varied expression patterns of these genes under different photoperiod suggest their potential involvement in the photoperiodic regulation of flowering in mung bean. Additionally, phenotypic analysis of transgenic Arabidopsis plants overexpressing VrFT1 revealed higher expression levels under SD conditions and predicted its role in promoting flowering. These results provide valuable insights into the evolution and function of PEBP genes in mung bean and lay the foundation for further research on their regulatory mechanisms and potential applications in mung bean improvement.

Systematical characterization of Rab7 gene family in Gossypium and potential functions of GhRab7B3-A gene in drought tolerance

BACKGROUND

Cotton serves as a primary source of natural fibers crucial for the textile industry. However, environmental elements such as drought have posed challenges to cotton cultivation, resulting in adverse impacts on both production and fiber quality. Improving cotton's resilience to drought could mitigate yield losses and foster the expansion of cotton farming. Rab7 protein, widely present in organisms, controls the degradation and recycling of cargo, and has a potential role in biotic and abiotic tolerance. However, comprehensive exploration of the Rab7 gene family in Gossypium remains scarce.

RESULTS

Herein, we identified a total of 10, 10, 20, and 20 Rab7 genes through genome-wide analysis in Gossypium arboreum, Gossypium raimondii, Gossypium hirsutum, and Gossypium barbadense, respectively. Collinearity analysis unveiled the pivotal role of whole genome or segmental duplication events in the expansion of GhRab7s. Study of gene architecture, conserved protein motifs, and domains suggested the conservation of structure and function throughout evolution. Exploration of cis-regulatory elements revealed the responsiveness of GhRab7 genes to abiotic stress, corroborated by transcriptome analysis under diverse environmental stresses. Notably, the greatly induced expression of GhRab7B3-A under drought treatment prompted us to investigate its function through virus-induced gene silencing (VIGS) assays. Silencing GhRab7B3-A led to exacerbated dehydration and wilting compared with the control. Additionally, inhibition of stomatal closure, antioxidant enzyme activities and expression patterns of genes responsive to abiotic stress were observed in GhRab7B3-A silenced plants.

CONCLUSIONS

This study sheds light on Rab7 members in cotton, identifies a gene linked to drought stress, and paves the way for additional investigation of Rab7 genes associated with drought stress tolerance.

Decrease in purifying selection pressures on wheat homoeologous genes: tetraploidization versus hexaploidization

A series of polyploidizations in higher-order polyploids is the main event affecting gene content in a genome. Each polyploidization event can lead to massive functional divergence because of the subsequent decrease in selection pressure on duplicated genes; however, the causal relationship between multiple rounds of polyploidization and the functional divergence of duplicated genes is poorly understood. We focused on the Triticum-Aegilops complex lineage and compared selection pressure before and after tetraploidization and hexaploidization events. Although both events led to decreased selection pressure on homoeologous gene pairs (compared with diploids and tetraploids), the initial tetraploidization had a greater impact on selection pressure on homoeologous gene pairs than did subsequent hexaploidization. Consistent with this, selection pressure on expression patterns for the initial event relaxed more than those for the subsequent event. Surprisingly, the decreased selection pressure on these homoeologous genes was independent of the existence of in-paralogs within the same subgenome. Wheat homoeologous pairs had different evolutionary consequences compared with orthologs related to other mechanisms (ancient allopolyploidization, ancient autopolyploidization, and small-scale duplication). Furthermore, tetraploidization and hexaploidization also seemed to have different evolutionary consequences. This suggests that homoeologous genes retain unique functions, including functions that are unlikely to be preserved in genes generated by the other duplication mechanisms. We found that their unique functions differed between tetraploidization and hexaploidization (e.g., reproductive and chromosome segregation processes). These findings imply that the substantial number of gene pairs resulting from multiple allopolyploidization events, especially initial tetraploidization, may have been a unique source of functional divergence.

Evolution of drought and frost responses in cool season grasses (Pooideae): was drought tolerance a precursor to frost tolerance?

Frost tolerance has evolved many times independently across flowering plants. However, conservation of several frost tolerance mechanisms among distant relatives suggests that apparently independent entries into freezing climates may have been facilitated by repeated modification of existing traits ('precursor traits'). One possible precursor trait for freezing tolerance is drought tolerance, because palaeoclimatic data suggest plants were exposed to drought before frost and several studies have demonstrated shared physiological and genetic responses to drought and frost stress. Here, we combine ecophysiological experiments and comparative analyses to test the hypothesis that drought tolerance acted as a precursor to frost tolerance in cool-season grasses (Pooideae). Contrary to our predictions, we measured the highest levels of frost tolerance in species with the lowest ancestral drought tolerance, indicating that the two stress responses evolved independently in different lineages. We further show that drought tolerance is more evolutionarily labile than frost tolerance. This could limit our ability to reconstruct the order in which drought and frost responses evolved relative to each other. Further research is needed to determine whether our results are unique to Pooideae or general for flowering plants.

Endosomal membrane budding patterns in plants

Multivesicular endosomes (MVEs) sequester membrane proteins destined for degradation within intralumenal vesicles (ILVs), a process mediated by the membrane-remodeling action of Endosomal Sorting Complex Required for Transport (ESCRT) proteins. In Arabidopsis, endosomal membrane constriction and scission are uncoupled, resulting in the formation of extensive concatenated ILV networks and enhancing cargo sequestration efficiency. Here, we used a combination of electron tomography, computer simulations, and mathematical modeling to address the questions of when concatenated ILV networks evolved in plants and what drives their formation. Through morphometric analyses of tomographic reconstructions of endosomes across yeast, algae, and various land plants, we have found that ILV concatenation is widespread within plant species, but only prevalent in seed plants, especially in flowering plants. Multiple budding sites that require the formation of pores in the limiting membrane were only identified in hornworts and seed plants, suggesting that this mechanism has evolved independently in both plant lineages. To identify the conditions under which these multiple budding sites can arise, we used particle-based molecular dynamics simulations and found that changes in ESCRT filament properties, such as filament curvature and membrane binding energy, can generate the membrane shapes observed in multiple budding sites. To understand the relationship between membrane budding activity and ILV network topology, we performed computational simulations and identified a set of membrane remodeling parameters that can recapitulate our tomographic datasets.

Genome-wide identification and expression analysis of CASPL gene family in Zea mays (L.)

Casparian strip membrane domain proteins like (CASPL), exhibit profound associations with root development, stress responsiveness and mineral element uptake in plants. Nonetheless, a comprehensive bioinformatics analysis of the ZmCASPL gene family in maize remains unreported. In the study, we have identified 47 ZmCASPL members at the whole-genome level, systematically classifying them into six distinct groups. Furthermore, our analysis revealed that the same group of ZmCASPL contains similar gene structures and conserved motifs. Duplication events showed whole genome duplication (WGD) and tandem duplication (TD) contribute to the generation of the ZmCASPL gene family together in maize, but the former plays a more prominent role. Furthermore, we observed that most ZmCASPL genes contain MYB-binding sites (CAACCA), which are associated with the Casparian strip. Utilizing RNA-seq data, we found that ZmCASPL21 and ZmCASPL47 are specifically highly expressed only in the roots. This finding implies that ZmCASPL21 and ZmCASPL47 may be involved in the Casparian strip development. Additionally, RNA-seq analysis illuminated that drought, salt, heat, cold stresses, low nitrogen and phosphorus conditions, as well as pathogen infection, significantly impact the expression patterns of ZmCASPL genes. RT-qPCR revealed that ZmCASPL 5/13/25/44 genes showed different expression patterns under PEG and NaCl treatments. Collectively, these findings provide a robust theoretical foundation for further investigations into the functional roles of the ZmCASPL gene family in maize.

Genomic Identification and Expression Analysis of Regulator of Chromosome Condensation 1-Domain Protein Family in Maize

Abiotic stress affects the growth and development of maize (Zea mays). The regulator of chromosome condensation 1 (RCC1)-containing proteins (RCPs) plays crucial roles in plant growth and development and response to abiotic stresses. However, a comprehensive analysis of the maize RCP family has not been reported in detail. This study presents a systematic bioinformatics analysis of the ZmRCP family, identifying a total of 30 members distributed across nine chromosomes. The physicochemical properties and cis-acting elements in the promoters of ZmRCP members are predicted. The results of subcellular localization showed that ZmRCP3 and ZmRCP10 are targeted to mitochondria and ZmRCP2 is localized in the nucleus. A heatmap of expression levels among family members under abiotic stress conditions revealed varying degrees of induced expression, and the expression levels of 10 ZmRCP members were quantified using RT-qPCR under abiotic stress and plant hormone treatments. The results showed that ZmRCP members exhibit induced or inhibited responses to these abiotic stresses and plant hormones. These results contribute to a better understanding of the evolutionary history and potential role of the ZmRCP family in mediating responses to abiotic stress in maize.

Genome-Wide Identification and Analysis of Phospholipase C Gene Family Reveals Orthologs, Co-Expression Networks, and Expression Profiling Under Abiotic Stress in Sorghum bicolor

Phospholipase C (PLC) is an essential enzyme involved in lipid signaling pathways crucial for regulating plant growth and responding to environmental stress. In sorghum, 11 PLC genes have been identified, comprising 6 PI-PLCs and 5 NPCs. Through phylogenetic and interspecies collinearity analyses, structural similarities between SbPLCs and ZmPLCs proteins have been observed, with a particularly strong collinearity between SbPLCs and OsPLCs. Promoter function analysis has shown that SbPLCs are significantly enriched under abiotic stress and hormonal stimuli, like ABA, jasmonic acid, drought, high temperature, and salt. Gene co-expression networks, constructed using a weighted gene co-expression network analysis (WGCNA), highlight distinct expression patterns of SbPLC1, SbPLC3a, and SbPLC4 in response to abiotic stress, providing further insights into the expression patterns and interactions of SbPLCs under various environmental stimuli. qRT-PCR results reveal variations in expression levels among most SbPLCs members under different stress conditions (drought, NaCl, NaHCO3), hormone treatments (ABA), and developmental stages, indicating both specific and overlapping expression patterns. This comprehensive analysis offers valuable insights into the roles of SbPLCs in sorghum, shedding light on their specific expression patterns, regulatory elements, and protein interactions across different environmental stimuli and developmental stages.

Gravitropic Gene Expression Divergence Associated With Adaptation to Contrasting Environments in an Australian Wildflower

Plants adapt to their local environment through complex interactions between genes, gene networks and hormones. Although the impact of gene expression on trait regulation and evolution has been recognised for many decades, its role in the evolution of adaptation is still a subject of intense exploration. We used a Multi-parent Advanced Generation Inter-Cross (MAGIC) population, which we derived from crossing multiple parents from two distinct coastal ecotypes of an Australia wildflower, Senecio lautus. We focused on studying the contrasting gravitropic behaviours of these ecotypes, which have evolved independently multiple times and show strong responses to natural selection in field experiments, emphasising the role of natural selection in their evolution. Here, we investigated how gene expression differences have contributed to the adaptive evolution of gravitropism. We studied gene expression in 60 pools at five time points (30, 60, 120, 240 and 480 min) after rotating half of the pools 90°. We found 428 genes with differential expression in response to the 90° rotation treatment. Of these, 81 genes (~19%) have predicted functions related to the plant hormones auxin and ethylene, which are crucial for the gravitropic response. By combining insights from Arabidopsis mutant studies and analysing our gene networks, we propose a preliminary model to explain the differences in gravitropism between ecotypes. This model suggests that the differences arise from changes in the transport and availability of the two hormones auxin and ethylene. Our findings indicate that the genetic basis of adaptation involves interconnected signalling pathways that work together to give rise to new ecotypes.

Genomic convergence in terrestrial root plants through tandem duplication in response to soil microbial pressures

Despite increasing reports of convergent adaptation, evidence for genomic convergence across diverse species worldwide is lacking. Here, our study of 205 Archaeplastida genomes reveals evidence of genomic convergence through tandem duplication (TD) across different lineages of root plants despite their genomic diversity. TD-derived genes, notably prevalent in trees with developed root systems embedded in soil, are enriched in enzymatic catalysis and biotic stress responses, suggesting adaptations to environmental pressures. Correlation analyses suggest that many factors, particularly those related to soil microbial pressures, are significantly associated with TD dynamics. Conversely, flora transitioned to aquatic, parasitic, halophytic, or carnivorous lifestyles-reducing their interaction with soil microbes-exhibit a consistent decline in TD frequency. This trend is further corroborated in mangroves that independently adapted to hypersaline intertidal soils, characterized by diminished microbial activity. Our findings propose TD-driven genomic convergence as a widespread adaptation to soil microbial pressures among terrestrial root plants.

Expression and functional divergence of a type-A response regulator paralog pair formed by dispersed duplication during Populus deltoides evolution

Gene duplication and divergence are essential to plant evolution. The Arabidopsis type-A response regulator (ARR) family, negative regulators in cytokinin signaling, exemplifies gene expansion and differential retention. Despite extensive research, the understanding of type-A RR homologs in woody plants remains limited. In this study, the evolution history of type-A RR gene families across four rosids and one monocot has been comprehensively investigated. Focusing on Populus deltoides, a unique pair of dispersed duplicates, PdRR8 and PdFERR, is identified, and their duplication is estimated to have occurred in the common ancestor of the four rosids. The duplication remnants corresponding to PdRR8 have been retained in all rosids but the counterpart of PdFERR has been lost. In poplar, PdRR8 shows the highest expression levels in leaves, while PdFERR is specifically expressed in female floral buds. Among various external stimuli, cold strongly represses PdRR8 promoter activity, whereas 6-BA markedly inhibits that of PdFERR. Overexpression of PdRR8 in the Arabidopsis arr16arr17 double-mutant fully complements the reduced hydrotropic response. In contrast, PdFERR fails to rescue the hydrotropic defects of the mutant. Results of evolutionary, expression and functional analyses indicate that PdRR8, rather than PdFERR, is the true ortholog of the ARR16-ARR17 paralogs. Though PdRR8 and PdFERR originate from a common ancestral gene and evolve under strong negative selection, these two dispersed duplicates have exhibited differential expression and some degree of functional divergence.

Phylogenomic Analysis and Functional Characterization of the APETALA2/Ethylene-Responsive Factor Transcription Factor Across Solanaceae

The AP2/ERF family constitutes one of the largest groups of transcription factors in the Solanaceae. AP2/ERF contributes to various plant biological processes, including growth, development, and responses to various stresses. The origins and functional diversification of AP2/ERF within the Solanaceae family remain poorly understood, primarily because of the complex interactions between whole-genome duplications (WGDs) and tandem duplications. In this study, a total of 1282 AP2/ERF proteins are identified from 7 Solanaceae genomes. The amplification of AP2/ERF genes was driven not only by WGDs but also by the presence of clusters of tandem duplicated genes. The conservation of synteny across different chromosomes provides compelling evidence for the impact of the WGD event on the distribution pattern of AP2/ERF genes. Distinct expression patterns suggest that the multiple copies of AP2/ERF genes evolved in different functional directions, catalyzing the diversification of roles among the duplicated genes, which was of great significance for the adaptability of Solanaceae. Gene silencing and overexpression assays suggest that ERF-1 members' role in regulating the timing of floral initiation in C. annuum. Our findings provide insights into the genomic origins, duplication events, and function divergence of the Solanaceae AP2/ERF.

Expression analysis of the apple HSP70 gene family in abiotic stress and phytohormones and expression validation of candidate MdHSP70 genes

Heat shock protein 70 (HSP70) is one kind of molecular chaperones which are widely found in organisms, and its members are highly conserved among each other, with important roles in plant growth and development. In this study, 56 HSP70 genes were identified from the apple genome database. Analysis of gene duplication events showed that tandem and segmental duplication events play an important role in promoting the amplification of the MdHSP70 gene family. Collinearity analysis showed that HSP70 family members of apple were more closely related to HSP70 family members of Arabidopsis, tomato and soybean. The promoter region of the apple HSP70 genes contains a large number of cis-acting elements in response to hormones and stress. Tissue-specific expression analysis showed that some of the genes were associated with various stages of the apple growth process. Codon preference analysis showed small differences between codon bases 1 and 3 in the apple HSP70 genome, and the codon base composition had a small effect on codon usage preference. The multiple expression patterns of the MdHSP70 gene suggested that MdHSP70 gene members play important roles in growth and development and in response to hormonal and abiotic stresses. The yeast two-hybrid (Y2H) demonstrated that MdHSP70-53 interacts with MdDVH24_032563. The qRT-PCR analysis showed that most MdHSP70 members' hormonal and abiotic stresses (MdHSP70-6, MdHSP70-26 and MdHSP70-45) appeared to be highly expressed. To further elucidate the function of MdHSP70 (6, 26, 45), we introduced them into tobacco to confirm subcellular locations and noted that these genes are located in the cytoplasm and cell membrane. This study serves as a theoretical basis for further studies of the MdHSP70 gene and helps to further investigate the functional characterization of MdHSP70 gene.

The biosynthesis of asiaticoside and madecassoside reveals tandem duplication-directed evolution of glycoside glycosyltransferases in the Apiales

Certain plant species within the Apiales order accumulate triterpenoid saponins that feature a distinctive glucose-glucose-rhamnose (G-G-R) sugar chain attached at the C-28 position of the pentacyclic triterpene skeleton. Until recently, the genomic basis underlying the biosynthesis and evolution of this sugar chain has remained elusive. In this study, we identified two novel glycoside glycosyltransferases (GGTs) that can sequentially install the sugar chain's second D-glucose and third L-rhamnose during the biosynthesis of asiaticoside and madecassoside, two representative G-G-R sugar chain-containing triterpenoid saponins produced by Centella asiatica. Enzymatic assays revealed the remarkable substrate promiscuity of the two GGTs and the key residues crucial for sugar-donor selectivity of the glucosyltransferase and rhamnosyltransferase. We further identified syntenic tandem gene duplicates of the two GGTs in the Apiaceae and Araliaceae families, suggesting a well-conserved genomic basis underlying sugar chain assembly that likely has evolved in the early ancestors of the Apiales order. Moreover, expression patterns of the two GGTs in pierced leaves of C. asiatica were found to be correlated with the production of asiaticoside and madecassoside, implying their involvement in host defense against herbivores and pathogens. Our work sheds light on the biosynthesis and evolution of complex saponin sugars, paving the way for future engineering of diverse bioactive triterpenoids with unique glycoforms.

Genome-Wide Identification of the Peanut ASR Gene Family and Its Expression Analysis under Abiotic Stress

Peanut (Arachis hypogaea L.) is one of the most important oil and food legume crops worldwide. ASR (abscisic acid, stress, ripening) plays extremely important roles in plant growth and development, fruit ripening, pollen development, and stress. Here, six ASR genes were identified in peanut. Structural and conserved motif analyses were performed to identify common ABA/WDS structural domains. The vast majority of ASR genes encoded acidic proteins, all of which are hydrophilic proteins and localized on mitochondria and nucleus, respectively. The cis-element analysis revealed that some cis-regulatory elements were related to peanut growth and development, hormone, and stress response. Under normal growth conditions, AhASR4 and AhASR5 were expressed in all tissues of peanut plants. Quantitative real-time PCR (qRT-PCR) results indicated that peanut ASR genes exhibited complex expression patterns in response to abiotic stress. Notably, under drought and cadmium (Cd) stress, the expression levels of AhASR4 and AhASR5 were significantly upregulated, suggesting that these genes may play a crucial role in the peanut plant's resistance to such stressors. These results provide a theoretical basis for studying the evolution, expression, and function of the peanut ASR gene family and will provide valuable information in the identification and screening of genes for peanut stress tolerance breeding.

Functional diversification within the heme-binding split-barrel family

Due to neofunctionalization, a single fold can be identified in multiple proteins that have distinct molecular functions. Depending on the time that has passed since gene duplication and the number of mutations, the sequence similarity between functionally divergent proteins can be relatively high, eroding the value of sequence similarity as the sole tool for accurately annotating the function of uncharacterized homologs. Here, we combine bioinformatic approaches with targeted experimentation to reveal a large multifunctional family of putative enzymatic and nonenzymatic proteins involved in heme metabolism. This family (homolog of HugZ (HOZ)) is embedded in the "FMN-binding split barrel" superfamily and contains separate groups of proteins from prokaryotes, plants, and algae, which bind heme and either catalyze its degradation or function as nonenzymatic heme sensors. In prokaryotes these proteins are often involved in iron assimilation, whereas several plant and algal homologs are predicted to degrade heme in the plastid or regulate heme biosynthesis. In the plant Arabidopsis thaliana, which contains two HOZ subfamilies that can degrade heme in vitro (HOZ1 and HOZ2), disruption of AtHOZ1 (AT3G03890) or AtHOZ2A (AT1G51560) causes developmental delays, pointing to important biological roles in the plastid. In the tree Populus trichocarpa, a recent duplication event of a HOZ1 ancestor has resulted in localization of a paralog to the cytosol. Structural characterization of this cytosolic paralog and comparison to published homologous structures suggests conservation of heme-binding sites. This study unifies our understanding of the sequence-structure-function relationships within this multilineage family of heme-binding proteins and presents new molecular players in plant and bacterial heme metabolism.