Identification, Classification, and Transcriptional Analysis of Rab GTPase Genes from Tomato (Solanum lycopersicum) Reveals Salt Stress Response Genes.

Salinity in plants generates an osmotic and ionic imbalance inside cells that compromises the viability of the plant. Rab GTPases, the largest family within the small GTPase superfamily, play pivotal roles as regulators of vesicular trafficking in plants, including the economically important and globally cultivated tomato (Solanum lycopersicum). Despite their significance, the specific involvement of these small GTPases in tomato vesicular trafficking and their role under saline stress remains poorly understood. In this work, we identified and classified 54 genes encoding Rab GTPases in cultivated tomato, elucidating their genomic distribution and structural characteristics. We conducted an analysis of duplication events within the S. lycopersicum genome, as well as an examination of gene structure and conserved motifs. In addition, we investigated the transcriptional profiles for these Rab GTPases in various tissues of cultivated and wild tomato species using microarray-based analysis. The results showed predominantly low expression in most of the genes in both leaves and vegetative meristem, contrasting with notably high expression levels observed in seedling roots. Also, a greater increase in gene expression in shoots from salt-tolerant wild tomato species was observed under normal conditions when comparing Solanum habrochaites, Solanum pennellii, and Solanum pimpinellifolium with S. lycopersicum. Furthermore, an expression analysis of Rab GTPases from Solanum chilense in leaves and roots under salt stress treatment were also carried out for their characterization. These findings revealed that specific Rab GTPases from the endocytic pathway and the trans-Golgi network (TGN) showed higher induction in plants exposed to saline stress conditions. Likewise, disparities in gene expression were observed both among members of the same Rab GTPase subfamily and between different subfamilies. Overall, this work emphasizes the high degree of conservation of Rab GTPases, their high functional diversification in higher plants, and the essential role in mediating salt stress tolerance and suggests their potential for further exploration of vesicular trafficking mechanisms in response to abiotic stress conditions.

The RabGAP Gene Family in Tomato (Solanum lycopersicum) and Wild Relatives: Identification, Interaction Networks, and Transcriptional Analysis during Plant Development and in Response to Salt Stress.

RabGTPase activating proteins (RabGAP) are responsible for directing the deactivation of vesicular trafficking master regulators associated to plant development, the RabGTPase proteins. Recently, RabGAPs were identified in Arabidopsis and rice, but studies were not yet reported in tomato. Herein, we identified 24 RabGAP-encoding genes in cultivated tomato (Solanum lycopersicum) and its wild relative genomes (Solanum pimpinellifolium and Solanum pennellii). We analyzed them based on their exon-intron structures, conserved protein motifs, putative subcellular localizations, phylogenetic and gene duplications analyses, interaction networks, and gene expression patterns in tomato. Phylogenetic relationship analysis also indicated that RabGAP family is classified into seven subclasses, of which subclasses I and II are plant-exclusive. Furthermore, segmental duplication events and positive evolutionary forces are associated with the maintenance of the number and function of their members. On the other hand, the protein-protein interaction networks on tomato suggested that members of subclasses I, II, and III could be associated to endocytic traffic routes. In addition, the qRT-PCR experiments in S. lycopersicum and Solanum chilense exposed to a salt stress treatment validated the differential expression patterns of 20 RabGAP genes in different tissues, development stages, and stress conditions obtained through extensive microarray-based analyses. This work suggests the critical role of RabGAP family in the context of intracellular vesicular trafficking in tomato, particularly under conditions of abiotic stress. It also contributes to the breeding programs associated with the development of crops tolerant to salt stress.

Cysteine-Rich Receptor-Like Kinase Gene Family Identification in the Phaseolus Genome and Comparative Analysis of Their Expression Profiles Specific to Mycorrhizal and Rhizobial Symbiosis.

Receptor-like kinases (RLKs) are conserved upstream signaling molecules that regulate several biological processes, including plant development and stress adaptation. Cysteine (C)-rich receptor-like kinases (CRKs) are an important class of RLK that play vital roles in disease resistance and cell death in plants. Genome-wide analyses of CRK genes have been carried out in Arabidopsis and rice, while functional characterization of some CRKs has been carried out in wheat and tomato in addition to Arabidopsis. A comprehensive analysis of the CRK gene family in leguminous crops has not yet been conducted, and our understanding of their roles in symbiosis is rather limited. Here, we report the comprehensive analysis of the PhaseolusCRK gene family, including identification, sequence similarity, phylogeny, chromosomal localization, gene structures, transcript expression profiles, and in silico promoter analysis. Forty-six CRK homologs were identified and phylogenetically clustered into five groups. Expression analysis suggests that PvCRK genes are differentially expressed in both vegetative and reproductive tissues. Further, transcriptomic analysis revealed that shared and unique CRK genes were upregulated during arbuscular mycorrhizal and rhizobial symbiosis. Overall, the systematic analysis of the PvCRK gene family provides valuable information for further studies on the biological roles of CRKs in various Phaseolus tissues during diverse biological processes, including Phaseolus-mycorrhiza/rhizobia symbiosis.