Plant NIGT1/HRS1/HHO Transcription Factors: Key Regulators with Multiple Roles in Plant Growth, Development, and Stress Responses

O-Glycosyltransferase Gene BnaC09.OGT Involved in Regulation of Unsaturated Fatty Acid Biosynthesis for Enhancing Osmotic Stress Tolerance in Brassica napus L

Osmotic stress is a major threaten to the growth and yield stability of Brassica napus. Post-translational modification with O-linked β-N-acetylglucosamine (O-GlcNAc) is ubiquitous in plants, and participates in a variety of signal transduction and metabolic regulation. However, studies on the role of O-GlcNAc transferase (OGT) in osmotic stress tolerance of plants are limited. In previous study, a O-glycosyltransferase, named BnaC09.OGT, was identified from the B. napus variety 'Zhongshuang 11' by yeast one hybrid with promoter of BnaA01.GPAT9. It was found that BnaC09.OGT localized in both nucleus and cytoplasm. The spatiotemporal expression pattern of BnaC09.OGT exhibited tissue specificity in developmental seed, especially in 15 days after pollination. In view of osmotic stress inducing, the BnaC09.OGT overexpression and knockout transgenic lines were constructed for biological function study. Phenotypic analysis of BnaC09.OGT overexpression seedlings demonstrated that BnaC09.OGT could enhance osmotic stress tolerance than WT and knockout lines in euphylla stage under 15% PEG6000 treatment after 7 days. In addition, compared with WT and knockout lines, overexpression of BnaC09.OGT had significantly higher activities of antioxidant enzymes (SOD and POD), higher content of soluble saccharide, and while significantly less content of malondialdehyde, proline and anthocyanidin under 15% PEG6000 treatment after 7 days. On the other hand, the unsaturated fatty acid content of BnaC09.OGT overexpression was significantly higher than that of WT and knockout lines, so it is speculated that the BnaC09.OGT could increase unsaturated fatty acid biosynthesis for osmotic stress tolerance by promoting the expression of BnaA01.GPAT9 in glycerolipid biosynthesis. In summary, the above results revealed that the function of BnaC09.OGT provides new insight for the analysis of the pathway of O-glycosylation in regulating osmotic stress tolerance in B. napus.

Role of GARP family transcription factors in the regulatory network for nitrogen and phosphorus acquisition

The GARP (Golden2, ARR-B, Psr1) family proteins with a conserved DNA-binding domain, called the B-motif, are plant-specific transcription factors involved in the regulation of various physiological processes. The GARP family proteins are divided into members that function as monomeric transcription factors, and members that function as transcription factors in the dimeric form, owing to the presence of a coiled-coil dimerization domain. Recent studies revealed that the dimer-forming GARP family members, which are further divided into the PHR1 and NIGT1 subfamilies, play critical roles in the regulation of phosphorus (P) and nitrogen (N) acquisition. In this review, we present a general overview of the GARP family proteins and discuss how several members of the PHR1 and NIGT1 subfamilies are involved in the coordinated acquisition of P and N in response to changes in environmental nutrient conditions, while mainly focusing on the recent findings that enhance our knowledge of the roles of PHR1 and NIGT1 in phosphate starvation signaling and nitrate signaling.

Haplotype-based phylogenetic analysis and population genomics uncover the origin and domestication of sweetpotato

The hexaploid sweetpotato (Ipomoea batatas) is one of the most important root crops worldwide. However, its genetic origin remains controversial, and its domestication history remains unknown. In this study, we used a range of genetic evidence and a newly developed haplotype-based phylogenetic analysis to identify two probable progenitors of sweetpotato. The diploid progenitor was likely closely related to Ipomoea aequatoriensis and contributed the B1 subgenome, IbT-DNA2, and the lineage 1 type of chloroplast genome to sweetpotato. The tetraploid progenitor of sweetpotato was most likely I. batatas 4x, which donated the B2 subgenome, IbT-DNA1, and the lineage 2 type of chloroplast genome. Sweetpotato most likely originated from reciprocal crosses between the diploid and tetraploid progenitors, followed by a subsequent whole-genome duplication. In addition, we detected biased gene exchanges between the subgenomes; the rate of B1 to B2 subgenome conversions was nearly three times higher than that of B2 to B1 subgenome conversions. Our analyses revealed that genes involved in storage root formation, maintenance of genome stability, biotic resistance, sugar transport, and potassium uptake were selected during the speciation and domestication of sweetpotato. This study sheds light on the evolution of sweetpotato and paves the way for improvement of this crop.

Transcriptome Profiling Reveals the Gene Network Responding to Low Nitrogen Stress in Wheat

As one of the essential nutrients for plants, nitrogen (N) has a major impact on the yield and quality of wheat worldwide. Due to chemical fertilizer pollution, it has become increasingly important to improve crop yield by increasing N use efficiency (NUE). Therefore, understanding the response mechanisms to low N (LN) stress is essential for the regulation of NUE in wheat. In this study, LN stress significantly accelerated wheat root growth, but inhibited shoot growth. Further transcriptome analysis showed that 8468 differentially expressed genes (DEGs) responded to LN stress. The roots and shoots displayed opposite response patterns, of which the majority of DEGs in roots were up-regulated (66.15%; 2955/4467), but the majority of DEGs in shoots were down-regulated (71.62%; 3274/4565). GO and KEGG analyses showed that nitrate reductase activity, nitrate assimilation, and N metabolism were significantly enriched in both the roots and shoots. Transcription factor (TF) and protein kinase analysis showed that genes such as MYB-related (38/38 genes) may function in a tissue-specific manner to respond to LN stress. Moreover, 20 out of 107 N signaling homologous genes were differentially expressed in wheat. A total of 47 transcriptome datasets were used for weighted gene co-expression network analysis (17,840 genes), and five TFs were identified as the potential hub regulatory genes involved in the response to LN stress in wheat. Our findings provide insight into the functional mechanisms in response to LN stress and five candidate regulatory genes in wheat. These results will provide a basis for further research on promoting NUE in wheat.

Transcriptional survey of abiotic stress response in maize (Zea mays) in the level of gene co-expression network and differential gene correlation analysis

Abstract. Maize may be exposed to several abiotic stresses in the field. Therefore, identifying the tolerance mechanisms of natural field stress is mandatory. Gene expression data of maize upon abiotic stress were collected, and 560 differentially expressed genes (DEGs) were identified through meta-analysis. The most significant gene ontology terms in up-regulated genes were 'response to abiotic stress' and 'chitinase activity'. 'Phosphorelay signal transduction system' was the most significant enriched biological process in down-regulated DEGs. The co-expression analysis unveiled seven modules of DEGs, with a notable positive correlation between the modules and abiotic stress. Furthermore, the statistical significance was strikingly high for the turquoise, green and yellow modules. The turquoise group played a central role in orchestrating crucial adaptations in metabolic and stress response pathways in maize when exposed to abiotic stress. Within three up-regulated modules, Zm.7361.1.A1_at, Zm.10386.1.A1_a_at and Zm.10151.1.A1_at emerged as hub genes. These genes might introduce novel candidates implicated in stress tolerance mechanisms, warranting further comprehensive investigation and research. In parallel, the R package glmnet was applied to fit a logistic LASSO regression model on the DEGs profile to select candidate genes associated with abiotic responses in maize. The identified hub genes and LASSO regression genes were validated on an independent microarray dataset. Additionally, Differential Gene Correlation Analysis (DGCA) was performed on LASSO and hub genes to investigate the gene-gene regulatory relationship. The P value of DGCA of 16 pairwise gene comparisons was lower than 0.01, indicating a gene-gene significant change in correlation between control and abiotic stress. Integrated weighted gene correlation network analysis and logistic LASSO analysis revealed Zm.11185.1.S1_at, Zm.2331.1.S1_x_at and Zm.17003.1.S1_at. Notably, these 3 genes were identified in the 16 gene-pair comparisons. This finding highlights the notable significance of these genes in the abiotic stress response. Additional research into maize stress tolerance may focus on these three genes.

Integrating genome-wide association and transcriptome analysis to provide molecular insights into heterophylly and eco-adaptability in woody plants

Heterophylly is regard as an important adaptive mechanism in response to different environments within plants. However, the genetic mechanisms responsible for heterophylly in woody plants are still poorly understood. Herein, the divergence of heterophyllous leaves was investigated at morphogenesis and using microdissection and physiological indexes in paper mulberry, and the genetic basis of heterophylly was further revealed combined with genome-wide association study (GWAS), transcriptome analysis and weighted gene coexpression network analysis (WGCNA). Our results revealed that the flavonoid content and antioxidant activity increased gradually from the entire leaf to the palmatisect leaf, while the hormone content and net photosynthetic rate decreased. Through GWAS and transcriptome analysis, a total of 98 candidate genes and 2338 differentially expressed genes associated with heterophylly were identified. Importantly, we uncovered critical variations in the candidate genes Bp07g0981 (WOX) and Bp07g0920 (HHO), along with significant differences in haplotypes and expression levels among heterophyllous leaves. Our results also suggested that the genes involved in hormone signaling pathways, antioxidant activity, and flavonoid metabolism might be closely related to the heterophylly of paper mulberry, which could account for the physiological data. Indeed, CR-wox mutant lines showed significant changes in leaf phenotypes, and differential expression profile analysis also highlighted the expression of genes related to phytohormones and transcription factors. Together, the genetic variations and candidate genes detected in this study provide novel insights into the genetic mechanism of heterophylly, and would improve the understanding of eco-adaptability in heterophyllous woody plants.

Finding Balance in Adversity: Nitrate Signaling as the Key to Plant Growth, Resilience, and Stress Response

To effectively adapt to changing environments, plants must maintain a delicate balance between growth and resistance or tolerance to various stresses. Nitrate, a significant inorganic nitrogen source in soils, not only acts as an essential nutrient but also functions as a critical signaling molecule that regulates multiple aspects of plant growth and development. In recent years, substantial advancements have been made in understanding nitrate sensing, calcium-dependent nitrate signal transmission, and nitrate-induced transcriptional cascades. Mounting evidence suggests that the primary response to nitrate is influenced by environmental conditions, while nitrate availability plays a pivotal role in stress tolerance responses. Therefore, this review aims to provide an overview of the transcriptional and post-transcriptional regulation of key components in the nitrate signaling pathway, namely, NRT1.1, NLP7, and CIPK23, under abiotic stresses. Additionally, we discuss the specificity of nitrate sensing and signaling as well as the involvement of epigenetic regulators. A comprehensive understanding of the integration between nitrate signaling transduction and abiotic stress responses is crucial for developing future crops with enhanced nitrogen-use efficiency and heightened resilience.

NIGT1 represses plant growth and mitigates phosphate starvation signaling to balance the growth response tradeoff in rice

Inorganic phosphate (Pi) availability is an important factor which affects the growth and yield of crops, thus an appropriate and effective response to Pi fluctuation is critical. However, how crops orchestrate Pi signaling and growth under Pi starvation conditions to optimize the growth defense tradeoff remains unclear. Here we show that a Pi starvation-induced transcription factor NIGT1 (NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1) controls plant growth and prevents a hyper-response to Pi starvation by directly repressing the expression of growth-related and Pi-signaling genes to achieve a balance between growth and response under a varying Pi environment. NIGT1 directly binds to the promoters of Pi starvation signaling marker genes, like IPS1, miR827, and SPX2, under Pi-deficient conditions to mitigate the Pi-starvation responsive (PSR). It also directly represses the expression of vacuolar Pi efflux transporter genes VPE1/2 to regulate plant Pi homeostasis. We further demonstrate that NIGT1 constrains shoot growth by repressing the expression of growth-related regulatory genes, including brassinolide signal transduction master regulator BZR1, cell division regulator CYCB1;1, and DNA replication regulator PSF3. Our findings reveal the function of NIGT1 in orchestrating plant growth and Pi starvation signaling, and also provide evidence that NIGT1 acts as a safeguard to avoid hyper-response during Pi starvation stress in rice.

Integrated transcriptomic and metabolomic analysis reveals the effects of polyploidization on the lignin content and metabolic pathway in Eucalyptus

BACKGROUND

Lignin is a major restriction factor for the industrial production of biomass resources, such as pulp and bioenergy. Eucalyptus is one of the most important sources of pulp and bioenergy. After polyploidization, the lignin content of forest trees is generally reduced, which is considered a beneficial genetic improvement. However, the differences in the lignin content between triploid and diploid Eucalyptus and the underlying regulatory mechanism are still unclear.

RESULTS

We conducted a comprehensive analysis at the phenotypic, transcriptional and metabolite levels between Eucalyptus urophylla triploids and diploids to reveal the effects of polyploidization on the lignin content and lignin metabolic pathway. The results showed that the lignin content of Eucalyptus urophylla triploid stems was significantly lower than that of diploids. Lignin-related metabolites were differentially accumulated between triploids and diploids, among which coniferaldehyde, p-coumaryl alcohol, sinapaldehyde and coniferyl alcohol had significant positive correlations with lignin content, indicating that they might be primarily contributing metabolites. Most lignin biosynthetic genes were significantly downregulated, among which 11 genes were significantly positively correlated with the lignin content and above metabolites. Furthermore, we constructed a co-expression network between lignin biosynthetic genes and transcription factors based on weighted gene co-expression network analysis. The network identified some putative orthologues of secondary cell wall (SCW)-related transcription factors, among which MYB52, MYB42, NAC076, and LBD15 were significantly downregulated in Eucalyptus urophylla triploids. In addition, potential important transcription factors, including HSL1, BEE3, HHO3, and NAC046, also had high degrees of connectivity and high edge weights with lignin biosynthetic genes, indicating that they might also be involved in the variation of lignin accumulation between triploid and diploid Eucalyptus urophylla.

CONCLUSIONS

The results demonstrated that some lignin-related metabolites, lignin biosynthetic genes and transcription factors in Eucalyptus urophylla triploids may be relatively sensitive in response to the polyploidization effect, significantly changing their expression levels, which ultimately correlated with the varied lignin content. The analysis of the underlying formation mechanism could provide beneficial information for the development and utilization of polyploid biomass resources, which will be also valuable for genetic improvement in other bioenergy plants.

Haplotype-Resolution Transcriptome Analysis Reveals Important Responsive Gene Modules and Allele-Specific Expression Contributions under Continuous Salt and Drought in Camellia sinensis

The tea plant, Camellia sinensis (L.) O. Kuntze, is one of the most important beverage crops with significant economic and cultural value. Global climate change and population growth have led to increased salt and drought stress, negatively affecting tea yield and quality. The response mechanism of tea plants to these stresses remains poorly understood due to the lack of reference genome-based transcriptional descriptions. This study presents a high-quality genome-based transcriptome dynamic analysis of C. sinensis' response to salt and drought stress. A total of 2244 upregulated and 2164 downregulated genes were identified under salt and drought stress compared to the control sample. Most of the differentially expression genes (DEGs) were found to involve divergent regulation processes at different time points under stress. Some shared up- and downregulated DEGs related to secondary metabolic and photosynthetic processes, respectively. Weighted gene co-expression network analysis (WGCNA) revealed six co-expression modules significantly positively correlated with C. sinensis' response to salt or drought stress. The MEpurple module indicated crosstalk between the two stresses related to ubiquitination and the phenylpropanoid metabolic regulation process. We identified 1969 salt-responsive and 1887 drought-responsive allele-specific expression (ASE) genes in C. sinensis. Further comparison between these ASE genes and tea plant heterosis-related genes suggests that heterosis likely contributes to the adversity and stress resistance of C. sinensis. This work offers new insight into the underlying mechanisms of C. sinensis' response to salt and drought stress and supports the improved breeding of tea plants with enhanced salt and drought tolerance.

Genome-Wide Identification and Expression Analysis of AS2 Genes in Brassica rapa Reveal Their Potential Roles in Abiotic Stress

The ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES (AS2/LOB) gene family plays a pivotal role in plant growth, induction of phytohormones, and the abiotic stress response. However, the AS2 gene family in Brassica rapa has yet to be investigated. In this study, we identified 62 AS2 genes in the B. rapa genome, which were classified into six subfamilies and distributed across 10 chromosomes. Sequence analysis of BrAS2 promotors showed that there are several typical cis-elements involved in abiotic stress tolerance and stress-related hormone response. Tissue-specific expression analysis showed that BrAS2-47 exhibited ubiquitous expression in all tissues, indicating it may be involved in many biological processes. Gene expression analysis showed that the expressions of BrAS2-47 and BrAS2-10 were significantly downregulated under cold stress, heat stress, drought stress, and salt stress, while BrAS2-58 expression was significantly upregulated under heat stress. RT-qPCR also confirmed that the expression of BrAS2-47 and BrAS2-10 was significantly downregulated under cold stress, drought stress, and salt stress, and in addition BrAS2-56 and BrAS2-4 also changed significantly under the three stresses. In addition, protein-protein interaction (PPI) network analysis revealed that the Arabidopsis thaliana genes AT5G67420 (homologous gene of BrAS2-47 and BrAS2-10) and AT3G49940 (homologous gene of BrAS2-58) can interact with NIN-like protein 7 (NLP7), which has been previously reported to play a role in resistance to adverse environments. In summary, our findings suggest that among the BrAS2 gene family, BrAS2-47 and BrAS2-10 have the most potential for the regulation of abiotic stress tolerance. These results will facilitate future functional investigations of BrAS2 genes in B. rapa.

Root and Leaf Anatomy, Ion Accumulation, and Transcriptome Pattern under Salt Stress Conditions in Contrasting Genotypes of Sorghum bicolor

Roots from salt-susceptible ICSR-56 (SS) sorghum plants display metaxylem elements with thin cell walls and large diameter. On the other hand, roots with thick, lignified cell walls in the hypodermis and endodermis were noticed in salt-tolerant CSV-15 (ST) sorghum plants. The secondary wall thickness and number of lignified cells in the hypodermis have increased with the treatment of sodium chloride stress to the plants (STN). Lignin distribution in the secondary cell wall of sclerenchymatous cells beneath the lower epidermis was higher in ST leaves compared to the SS genotype. Casparian thickenings with homogenous lignin distribution were observed in STN roots, but inhomogeneous distribution was evident in SS seedlings treated with sodium chloride (SSN). Higher accumulation of K⁺ and lower Na⁺ levels were noticed in ST compared to the SS genotype. To identify the differentially expressed genes among SS and ST genotypes, transcriptomic analysis was carried out. Both the genotypes were exposed to 200 mM sodium chloride stress for 24 h and used for analysis. We obtained 70 and 162 differentially expressed genes (DEGs) exclusive to SS and SSN and 112 and 26 DEGs exclusive to ST and STN, respectively. Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis unlocked the changes in metabolic pathways in response to salt stress. qRT-PCR was performed to validate 20 DEGs in each SSN and STN sample, which confirms the transcriptomic results. These results surmise that anatomical changes and higher K⁺/Na⁺ ratios are essential for mitigating salt stress in sorghum apart from the genes that are differentially up- and downregulated in contrasting genotypes.

Syntaxin of plants71 plays essential roles in plant development and stress response via regulating pH homeostasis

SYP71, a plant-specific Qc-SNARE with multiple subcellular localization, is essential for symbiotic nitrogen fixation in nodules in Lotus, and is implicated in plant resistance to pathogenesis in rice, wheat and soybean. Arabidopsis SYP71 is proposed to participate in multiple membrane fusion steps during secretion. To date, the molecular mechanism underlying SYP71 regulation on plant development remains elusive. In this study, we clarified that AtSYP71 is essential for plant development and stress response, using techniques of cell biology, molecular biology, biochemistry, genetics, and transcriptomics. AtSYP71-knockout mutant atsyp71-1 was lethal at early development stage due to the failure of root elongation and albinism of the leaves. AtSYP71-knockdown mutants, atsyp71-2 and atsyp71-3, had short roots, delayed early development, and altered stress response. The cell wall structure and components changed significantly in atsyp71-2 due to disrupted cell wall biosynthesis and dynamics. Reactive oxygen species homeostasis and pH homeostasis were also collapsed in atsyp71-2. All these defects were likely resulted from blocked secretion pathway in the mutants. Strikingly, change of pH value significantly affected ROS homeostasis in atsyp71-2, suggesting interconnection between ROS and pH homeostasis. Furthermore, we identified AtSYP71 partners and propose that AtSYP71 forms distinct SNARE complexes to mediate multiple membrane fusion steps in secretory pathway. Our findings suggest that AtSYP71 plays an essential role in plant development and stress response via regulating pH homeostasis through secretory pathway.

Ammonium Uptake, Mediated by Ammonium Transporters, Mitigates Manganese Toxicity in Duckweed, Spirodela polyrhiza

Nitrogen is an essential nutrient that affects all aspects of the growth, development and metabolic responses of plants. Here we investigated the influence of the two major sources of inorganic nitrogen, nitrate and ammonium, on the toxicity caused by excess of Mn in great duckweed, Spirodela polyrhiza. The revealed alleviating effect of ammonium on Mn-mediated toxicity, was complemented by detailed molecular, biochemical and evolutionary characterization of the species ammonium transporters (AMTs). Four genes encoding AMTs in S. polyrhiza, were classified as SpAMT1;1, SpAMT1;2, SpAMT1;3 and SpAMT2. Functional testing of the expressed proteins in yeast and Xenopus oocytes clearly demonstrated activity of SpAMT1;1 and SpAMT1;3 in transporting ammonium. Transcripts of all SpAMT genes were detected in duckweed fronds grown in cultivation medium, containing a physiological or 50-fold elevated concentration of Mn at the background of nitrogen or a mixture of nitrate and ammonium. Each gene demonstrated an individual expression pattern, revealed by RT-qPCR. Revealing the mitigating effect of ammonium uptake on manganese toxicity in aquatic duckweed S. polyrhiza, the study presents a comprehensive analysis of the transporters involved in the uptake of ammonium, shedding a new light on the interactions between the mechanisms of heavy metal toxicity and the regulation of the plant nitrogen metabolism.

Genome-Scale Investigation of GARP Family Genes Reveals Their Pivotal Roles in Nutrient Stress Resistance in Allotetraploid Rapeseed

The GARP genes are plant-specific transcription factors (TFs) and play key roles in regulating plant development and abiotic stress resistance. However, few systematic analyses of GARPs have been reported in allotetraploid rapeseed (Brassica napus L.) yet. In the present study, a total of 146 BnaGARP members were identified from the rapeseed genome based on the sequence signature. The BnaGARP TFs were divided into five subfamilies: ARR, GLK, NIGT1/HRS1/HHO, KAN, and PHL subfamilies, and the members within the same subfamilies shared similar exon-intron structures and conserved motif configuration. Analyses of the Ka/Ks ratios indicated that the GARP family principally underwent purifying selection. Several cis-acting regulatory elements, essential for plant growth and diverse biotic and abiotic stresses, were identified in the promoter regions of BnaGARPs. Further, 29 putative miRNAs were identified to be targeting BnaGARPs. Differential expression of BnaGARPs under low nitrate, ammonium toxicity, limited phosphate, deficient boron, salt stress, and cadmium toxicity conditions indicated their potential involvement in diverse nutrient stress responses. Notably, BnaA9.HHO1 and BnaA1.HHO5 were simultaneously transcriptionally responsive to these nutrient stresses in both hoots and roots, which indicated that BnaA9.HHO1 and BnaA1.HHO5 might play a core role in regulating rapeseed resistance to nutrient stresses. Therefore, this study would enrich our understanding of molecular characteristics of the rapeseed GARPs and will provide valuable candidate genes for further in-depth study of the GARP-mediated nutrient stress resistance in rapeseed.

Phytochrome interacting factor regulates stomatal aperture by coordinating red light and abscisic acid

Stomata are crucial valves coordinating the fixation of carbon dioxide by photosynthesis and water loss through leaf transpiration. Phytochrome interacting factors (PIFs) are negative regulators of red light responses that belong to the basic helix-loop-helix family of transcription factors. Here, we show that the rice (Oryza sativa) PIF family gene OsPIL15 acts as a negative regulator of stomatal aperture to control transpiration in rice. OsPIL15 reduces stomatal aperture by activating rice ABSCISIC ACID INSENSITIVE 5 (OsABI5), which encodes a critical positive regulator of ABSCISIC ACID (ABA) signaling in rice. Moreover, OsPIL15 interacts with the NIGT1/HRS1/HHO family transcription factor rice HRS1 HOMOLOG 3 (OsHHO3) to possibly enhance the regulation of stomatal aperture. Notably, we discovered that the maize (Zea mays) PIF family genes ZmPIF1 and ZmPIF3, which are homologous to OsPIL15, are also involved in the regulation of stomatal aperture in maize, indicating that PIF-mediated regulation of stomatal aperture may be conserved in the plant lineage. Our findings explain the molecular mechanism by which PIFs play a role in red-light-mediated stomatal opening, and demonstrate that PIFs regulate stomatal aperture by coordinating the red light and ABA signaling pathways.

Morphological, Transcriptome, and Hormone Analysis of Dwarfism in Tetraploids of Populus alba × P. glandulosa

Breeding for dwarfism is an important approach to improve lodging resistance. Here, we performed comparative analysis of the phenotype, transcriptome, and hormone contents between diploids and tetraploids of poplar 84K (Populus alba × P. glandulosa). Compared with diploids, the indole-3-acetic acid (IAA) and gibberellin (GA₃) contents were increased, whereas the jasmonic acid (JA) and abscisic acid (ABA) contents were decreased in tetraploids. RNA-sequencing revealed that differentially expressed genes (DEGs) in leaves of tetraploids were mainly involved in plant hormone pathways. Most DEGs associated with IAA and GA promotion of plant growth and development were downregulated, whereas most DEGs associated with ABA and JA promotion of plant senescence were upregulated. Weighted gene co-expression network analysis indicated that certain transcription factors may be involved in the regulation of genes involved in plant hormone pathways. Thus, the altered expression of some genes in the plant hormone pathways may lead to a reduction in IAA and GA contents, as well as an elevation in ABA and JA contents, resulting in the dwarfing of tetraploids. The results show that polyploidization is a complex biological process affected by multiple plant hormone signals, and it provides a foundation for further exploration of the mechanism of tetraploids dwarfing in forest trees.

MYB Transcription Factors Becoming Mainstream in Plant Roots

The function of the root system is crucial for plant survival, such as anchoring plants, absorbing nutrients and water from the soil, and adapting to stress. MYB transcription factors constitute one of the largest transcription factor families in plant genomes with structural and functional diversifications. Members of this superfamily in plant development and cell differentiation, specialized metabolism, and biotic and abiotic stress processes are widely recognized, but their roles in plant roots are still not well characterized. Recent advances in functional studies remind us that MYB genes may have potentially key roles in roots. In this review, the current knowledge about the functions of MYB genes in roots was summarized, including promoting cell differentiation, regulating cell division through cell cycle, response to biotic and abiotic stresses (e.g., drought, salt stress, nutrient stress, light, gravity, and fungi), and mediate phytohormone signals. MYB genes from the same subfamily tend to regulate similar biological processes in roots in redundant but precise ways. Given their increasing known functions and wide expression profiles in roots, MYB genes are proposed as key components of the gene regulatory networks associated with distinct biological processes in roots. Further functional studies of MYB genes will provide an important basis for root regulatory mechanisms, enabling a more inclusive green revolution and sustainable agriculture to face the constant changes in climate and environmental conditions.

Genome-Wide Identification and Characterization of GARP Transcription Factor Gene Family Members Reveal Their Diverse Functions in Tea Plant (Camellia sinensis)

Golden2, ARR-B, Psr1 (GARP) proteins are plant-specific transcription factors that play vital and diverse roles in plants. However, systematic research on the GARP gene family in plants, including tea plant (Camellia sinensis), is scarce. In this study, a total of 69 GARP genes were identified and characterized from the tea plant genome based on the B-motif sequence signature. The CsGARP genes were clustered into five subfamilies: PHR1/PHL1, KAN, NIGT1/HRS1/HHO, GLK and ARR-B subfamilies. The phylogenetic relationships, gene structures, chromosomal locations, conserved motifs and regulatory cis-acting elements of the CsGARP family members were comprehensively analyzed. The expansion of CsGARP genes occurred via whole-genome duplication/segmental duplication, proximal duplication, and dispersed duplication under purifying selective pressure. The expression patterns of the CsGARP genes were systematically explored from various perspectives: in different tissues during different seasons; in different leaf color stages of tea plant; under aluminum treatment and nitrogen treatment; and in response to abiotic stresses such as cold, drought and salt and to biotic stress caused by Acaphylla theae. The results demonstrate that CsGARP family genes are ubiquitously expressed and play crucial roles in the regulation of growth and development of tea plant and the responses to environmental stimuli. Collectively, these results not only provide valuable information for further functional investigations of CsGARPs in tea plant but also contribute to broadening our knowledge of the functional diversity of GARP family genes in plants.