Comparative Analysis of HSF Genes From Secale cereale and its Triticeae Relatives Reveal Ancient and Recent Gene Expansions

Genome-Wide Identification and Expression Analysis of the HSF Gene Family in Ammopiptanthus mongolicus

Ammopiptanthus mongolicus is an ancient remnant species from the Mediterranean displaying characteristics such as high-temperature tolerance, drought resistance, cold resistance, and adaptability to impoverished soil. In the case of high-temperature tolerance, heat shock transcription factors (HSFs) are integral transcriptional regulatory proteins exerting a critical role in cellular processes. Despite extensive research on the HSF family across various species, there has been no analysis specifically focused on A. mongolicus. In this study, we identified 24 members of the AmHSF gene family based on the genome database of A. mongolicus, which were unevenly distributed over 9 chromosomes. Phylogenetic analysis showed that these 24 members can be categorized into 5 primary classes consisting of a total of 13 subgroups. Analysis of the physical and chemical properties revealed significant diversity among these proteins. With the exception of the AmHSFB3 protein, which is localized in the cytoplasm, all other AmHSF proteins were found to be situated in the nucleus. Comparison of amino acid sequences revealed that all AmHSF proteins contain a conserved DNA-binding domains structure, and the DNA-binding domains and oligomerization domains of the AmHSF gene exhibit conservation with counterparts across diverse species; we investigated the collinearity of AmHSF genes in relation to those of three other representative species. Through GO enrichment analysis, evidence emerged that AmHSF genes are involved in heat stress responses and may be involved in multiple transcriptional regulatory pathways that coordinate plant growth and stress responses. Finally, through a comprehensive analysis using transcriptome data, we examined the expression levels of 24 AmHSFs under 45 °C. The results revealed significant differences in the expression profiles of AmHSFs at different time intervals during exposure to high temperatures, highlighting their crucial role in responding to heat stress. In summary, these results provide a better understanding of the role and regulatory mechanisms of HSF in the heat stress response of A. mongolicus, meanwhile also establishing a foundation for further exploration of the biological functions of AmHSF in the adversity response of A. mongolicus.

Identification of abiotic stress-responsive genes: a genome-wide analysis of the cytokinin response regulator gene family in rice

Response regulators (RRs) are implicated in various developmental processes as well as environmental responses by acting as either positive or negative regulators, and are crucial components of cytokinin signaling in plants. We characterized 36 RRs in rice (Oryza sativa L.; Os) using in silico analysis of publicly available data. A comprehensive analysis of OsRR family members covered their physicochemical properties, chromosomal distribution, subcellular localization, phylogeny, gene structure, distribution of conserved motifs and domains, and gene duplication events. Gene Ontology analysis indicated that 22 OsRR genes contribute mainly to the cytokinin response and signal transduction. Predicted cis-elements in RR promoter sequences related to phytohormones and abiotic stresses indicated that RRs are involved in hormonal and environmental responses, supporting previous studies. MicroRNA (miRNA) target analysis showed that 148 miRNAs target 29 OsRR genes. In some cases, multiple RRs are targets of the same miRNA group, and may be controlled by common stimulus responses. Based on the analysis of publicly available gene expression data, OsRR4, OsRR6, OsRR9, OsRR10, OsRR22, OsPRR73 and OsPRR95 were found to be involved in responses to abiotic stresses. Using quantitative reverse transcription polymerase chain reaction we confirmed that six of these RRs, namely OsRR4, OsRR6, OsRR9, OsRR10, OsRR22 and OsPRR73, are involved in the response to salinity, osmotic, alkaline and wounding stresses, and can potentially be used as models to understand molecular mechanisms underlying stress responsiveness.

Genome-Wide Identification and Evolutionary Analysis of Receptor-like Kinase Family Genes Provides Insights into Anthracnose Resistance of Dioscorea alata

Dioscorea alata, commonly known as "greater yam", is a vital crop in tropical and subtropical regions of the world, yet it faces significant threats from anthracnose disease, mainly caused by Colletotrichum gloeosporioides. However, exploring disease resistance genes in this species has been challenging due to the difficulty of genetic mapping resulting from the loss of the flowering trait in many varieties. The receptor-like kinase (RLK) gene family represents essential immune receptors in plants. In this study, genomic analysis revealed 467 RLK genes in D. alata. The identified RLKs were distributed unevenly across chromosomes, likely due to tandem duplication events. However, a considerable number of ancient whole-genome or segmental duplications dating back over 100 million years contributed to the diversity of RLK genes. Phylogenetic analysis unveiled at least 356 ancient RLK lineages in the common ancestor of Dioscoreaceae, which differentially inherited and expanded to form the current RLK profiles of D. alata and its relatives. The analysis of cis-regulatory elements indicated the involvement of RLK genes in diverse stress responses. Transcriptome analysis identified RLKs that were up-regulated in response to C. gloeosporioides infection, suggesting their potential role in resisting anthracnose disease. These findings provide novel insights into the evolution of RLK genes in D. alata and their potential contribution to disease resistance.

Transcriptomic analysis of the response of Avena sativa to Bacillus amyloliquefaciens DGL1

Introduction

Bacillus amyloliquefaciens DGL1, isolated from the arid sandy areas in Dagler, Qinghai Province, China, promotes the growth of Avena sativa variety "Qing Yan 1".

Methods

To elucidate the transcriptomic changes in the oat root system following interaction with DGL1 and to reveal the molecular mechanism by which DGL1 promotes oat growth, treatment and control groups of oat roots at 2, 4, 8, and 12 h after inoculation with a suspension of strain DGL1 were analyzed using Illumina high-throughput transcriptome sequencing technology. The differentially expressed genes were determined through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses, and the metabolic pathways and key genes were analyzed.

Results

The results showed that 7874, 13,392, 13,169, and 19,026 differentially expressed genes were significantly enriched in the glycolysis/gluconeogenesis pathway, amino acid metabolism, nitrogen metabolism, plant hormone signal transduction, and other related metabolic pathways in the oat roots at 2, 4, 8, and 12 h after inoculation with a DGL1 suspension. The GO and KEGG enrichment analyses revealed that the genes encoding plasma membrane ATPase, phosphoglycerate kinase gene PGK, ammonium transporter protein gene AMT, cellulose synthase gene CSLF6, and growth hormone response family gene IAA18 were significantly upregulated.

Discussion

It is hypothesized that the pro-growth mechanism of strain DGL1 in oats is the result of the coordination of multiple pathways through the promotion of oat energy metabolism, phytohormone signaling, secondary metabolite synthesis, and amino acid metabolism.

GhBRX.1, GhBRX.2, and GhBRX4.3 improve resistance to salt and cold stress in upland cotton

Introduction

Abiotic stress during growth readily reduces cotton crop yield. The different survival tactics of plants include the activation of numerous stress response genes, such as BREVIS RADIX (BRX).

Methods

In this study, the BRX gene family of upland cotton was identified and analyzed by bioinformatics method, three salt-tolerant and cold-resistant GhBRX genes were screened. The expression of GhBRX.1, GhBRX.2 and GhBRXL4.3 in upland cotton was silenced by virus-induced gene silencing (VIGS) technique. The physiological and biochemical indexes of plants and the expression of related stress-response genes were detected before and after gene silencing. The effects of GhBRX.1, GhBRX.2 and GhBRXL4.3 on salt and cold resistance of upland cotton were further verified.

Results and discussion

We discovered 12, 6, and 6 BRX genes in Gossypium hirsutum, Gossypium raimondii and Gossypium arboreum, respectively. Chromosomal localization indicated that the retention and loss of GhBRX genes on homologous chromosomes did not have a clear preference for the subgenomes. Collinearity analysis suggested that segmental duplications were the main force for BRX gene amplification. The upland cotton genes GhBRX.1, GhBRX.2 and GhBRXL4.3 are highly expressed in roots, and GhBRXL4.3 is also strongly expressed in the pistil. Transcriptome data and qRT‒PCR validation showed that abiotic stress strongly induced GhBRX.1, GhBRX.2 and GhBRXL4.3. Under salt stress and low-temperature stress conditions, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and the content of soluble sugar and chlorophyll decreased in GhBRX.1-, GhBRX.2- and GhBRXL4.3-silenced cotton plants compared with those in the control (TRV: 00). Moreover, GhBRX.1-, GhBRX.2- and GhBRXL4.3-silenced cotton plants exhibited greater malondialdehyde (MDA) levels than did the control plants. Moreover, the expression of stress marker genes (GhSOS1, GhSOS2, GhNHX1, GhCIPK6, GhBIN2, GhSnRK2.6, GhHDT4D, GhCBF1 and GhPP2C) decreased significantly in the three target genes of silenced plants following exposure to stress. These results imply that the GhBRX.1, GhBRX.2 and GhBRXL4.3 genes may be regulators of salt stress and low-temperature stress responses in upland cotton.

Pan-metagenome reveals the abiotic stress resistome of cigar tobacco phyllosphere microbiome

The important role of microbial associations in mediating plant protection and responses to abiotic stresses has been widely recognized. However, there have been limited studies on the functional profile of the phyllosphere microbiota from tobacco (Nicotiana tabacum), hindering our understanding of the mechanisms underlying stress resilience in this representative and easy-to-cultivate model species from the solanaceous family. To address this knowledge gap, our study employed shotgun metagenomic sequencing for the first time to analyze the genetic catalog and identify putative plant growth promoting bacteria (PGPB) candidates that confer abiotic stress resilience throughout the growth period of cigar tobacco in the phyllosphere. We identified abundant genes from specific bacterial lineages, particularly Pseudomonas, within the cigar tobacco phyllospheric microbiome. These genes were found to confer resilience against a wide range of stressors, including osmotic and drought stress, heavy metal toxicity, temperature perturbation, organic pollutants, oxidative stress, and UV light damage. In addition, we conducted a virome mining analysis on the metagenome to explore the potential roles of viruses in driving microbial adaptation to environmental stresses. Our results identified a total of 3,320 scaffolds predicted to be viral from the cigar tobacco phyllosphere metagenome, with various phages infecting Pseudomonas, Burkholderia, Enterobacteria, Ralstonia, and related viruses. Within the virome, we also annotated genes associated with abiotic stress resilience, such as alkaline phosphatase D (phoD) for nutrient solubilization and glutamate-5-semialdehyde dehydrogenase (proA) for osmolyte synthesis. These findings shed light on the unexplored roles of viruses in facilitating and transferring abiotic stress resilience in the phyllospheric microbiome through beneficial interactions with their hosts. The findings from this study have important implications for agricultural practices, as they offer potential strategies for harnessing the capabilities of the phyllosphere microbiome to enhance stress tolerance in crop plants.

Two-step model of paleohexaploidy, ancestral genome reshuffling and plasticity of heat shock response in Asteraceae

An ancient hexaploidization event in the most but not all Asteraceae plants, may have been responsible for shaping the genomes of many horticultural, ornamental, and medicinal plants that promoting the prosperity of the largest angiosperm family on the earth. However, the duplication process of this hexaploidy, as well as the genomic and phenotypic diversity of extant Asteraceae plants caused by paleogenome reorganization, are still poorly understood. We analyzed 11 genomes from 10 genera in Asteraceae, and redated the Asteraceae common hexaploidization (ACH) event ~70.7-78.6 million years ago (Mya) and the Asteroideae specific tetraploidization (AST) event ~41.6-46.2 Mya. Moreover, we identified the genomic homologies generated from the ACH, AST and speciation events, and constructed a multiple genome alignment framework for Asteraceae. Subsequently, we revealed biased fractionations between the paleopolyploidization produced subgenomes, suggesting the ACH and AST both are allopolyplodization events. Interestingly, the paleochromosome reshuffling traces provided clear evidence for the two-step duplications of ACH event in Asteraceae. Furthermore, we reconstructed ancestral Asteraceae karyotype (AAK) that has 9 paleochromosomes, and revealed a highly flexible reshuffling of Asteraceae paleogenome. Of specific significance, we explored the genetic diversity of Heat Shock Transcription Factors (Hsfs) associated with recursive whole-genome polyploidizations, gene duplications, and paleogenome reshuffling, and revealed that the expansion of Hsfs gene families enable heat shock plasticity during the genome evolution of Asteraceae. Our study provides insights on polyploidy and paleogenome remodeling for the successful establishment of Asteraceae, and is helpful for further communication and exploration of the diversification of plant families and phenotypes.

Genome mining reveals abiotic stress resistance genes in plant genomes acquired from microbes via HGT

Colonization by beneficial microbes can enhance plant tolerance to abiotic stresses. However, there are still many unknown fields regarding the beneficial plant-microbe interactions. In this study, we have assessed the amount or impact of horizontal gene transfer (HGT)-derived genes in plants that have potentials to confer abiotic stress resistance. We have identified a total of 235 gene entries in fourteen high-quality plant genomes belonging to phyla Chlorophyta and Streptophyta that confer resistance against a wide range of abiotic pressures acquired from microbes through independent HGTs. These genes encode proteins contributed to toxic metal resistance (e.g., ChrA, CopA, CorA), osmotic and drought stress resistance (e.g., Na+/proline symporter, potassium/proton antiporter), acid resistance (e.g., PcxA, ArcA, YhdG), heat and cold stress resistance (e.g., DnaJ, Hsp20, CspA), oxidative stress resistance (e.g., GST, PoxA, glutaredoxin), DNA damage resistance (e.g., Rad25, Rad51, UvrD), and organic pollutant resistance (e.g., CytP450, laccase, CbbY). Phylogenetic analyses have supported the HGT inferences as the plant lineages are all clustering closely with distant microbial lineages. Deep-learning-based protein structure prediction and analyses, in combination with expression assessment based on codon adaption index (CAI) further corroborated the functionality and expressivity of the HGT genes in plant genomes. A case-study applying fold comparison and molecular dynamics (MD) of the HGT-driven CytP450 gave a more detailed illustration on the resemblance and evolutionary linkage between the plant recipient and microbial donor sequences. Together, the microbe-originated HGT genes identified in plant genomes and their participation in abiotic pressures resistance indicate a more profound impact of HGT on the adaptive evolution of plants.

Role of the type-B authentic response regulator gene family in fragrant rice under alkaline salt stress

Globally, rice is being consumed as a main staple food and faces different kinds of biotic and abiotic stresses such drought, salinity, and pest attacks. Through the cytokinin signaling, Type-B authentic response regulators (ARR-Bs) respond positively towards the environmental stimuli. ARR-Bs are involved in abiotic stress tolerance and plant development but their molecular mechanisms in fragrant rice are still not fully explored. The current study showed the genome-wide characterization of OsARR-B genes under alkaline salt stress. Results showed that in total, 24 OsARR-B genes were found and divided into four subgroups on the basis of a phylogenetic analysis. These genes were located on all rice chromosomes except 8 and 10. Analysis of gene duplications, gene structure, cis-elements, protein-protein interactions, and miRNA were performed. Gene ontology analysis showed that OsARR-B genes are involved in plant development through the regulation of molecular functions, biological processes, and cellular components. Furthermore, 117 and 192 RNA editing sites were detected in chloroplast and mitochondrial genes, respectively, encoding proteins of OsARR-B. In chloroplast and mitochondrial genes, six and nine types of amino acid changes, respectively, were caused by RNA editing, showing that RNA editing has a role in the alkaline salt stress tolerance in fragrant rice. We also used a comparative transcriptome approach to study the gene expression changes in alkaline tolerant and susceptible genotypes. Under alkaline salt stress, OsARR-B5, OsARR-B7, OsARR-B9, OsARR-B10, OsARR-B16, OsARR-B22, and OsARR-B23 showed higher transcript levels in alkaline salt tolerant genotypes as compared to susceptible ones. Quantitative RT-PCR showed upregulation of gene expression in the alkaline tolerant genotypes under alkaline stress. Our study explored the gene expression profiling and RESs of two rice contrasting genotypes, which will help to understand the molecular mechanisms of alkaline salt tolerance in fragrant rice.