NBS-LRR (nucleotide-binding site and leucine-rich repeat) is one of the largest resistance gene families in plants. The completion of the genome sequencing of wild tomato Solanum pimpinellifolium provided an opportunity to conduct a comprehensive analysis of the NBS-LRR gene superfamily at the genome-wide level. In this study, gene identification, chromosome mapping, and phylogenetic analysis of the NBS-LRR gene family were analyzed using the bioinformatics methods. The results revealed 245 NBS-LRRs in total, similar to that in the cultivated tomato. These genes are unevenly distributed on 12 chromosomes, and ~59.6% of them form gene clusters, most of which are tandem duplications. Phylogenetic analysis divided the NBS-LRRs into 2 subfamilies (CNL-coiled-coil NBS-LRR and TNL-TIR NBS-LRR), and the expansion of the CNL subfamily was more extensive than the TNL subfamily. Novel conserved structures were identified through conserved motif analysis between the CNL and TNL subfamilies. Compared with the NBS-LRR sequences from the model plant Arabidopsis thaliana, wide genetic variation occurred after the divergence of S. pimpinellifolium and A thaliana. Species-specific expansion was also found in the CNL subfamily in S. pimpinellifolium. The results of this study provide the basis for the deeper analysis of NBS-LRR resistance genes and contribute to mapping and isolation of candidate resistance genes in S. pimpinellifolium.

Sugar transporter proteins (STPs) play an important role in plant growth and development and stress resistance. Pepper (Capsicum annuum L.) is a significant economic crop and is widely cultivated worldwide. However, the evolution and the roles of STP genes in the growth and development and in coping with abiotic stresses in pepper are poorly known. Here, we characterized STP gene family in pepper through integration of chromosomal location, gene structure, conserved motif, phylogeny, expression patterns in different tissues and abiotic stresses. Using bioinformatics-based methods, we identified 17 putative STP genes in pepper. Chromosome mapping indicated that they are unevenly distributed on 9 chromosomes and there are tandem duplication events. Gene structure analysis revealed that intron numbers among these CaSTP genes ranged from 2 to 5, except that CaSTP12 and CaSTP13 genes contained no introns. The phylogenetic tree of STP genes from pepper and other plant species revealed that STP genes were grouped into 4 subfamilies, suggesting that these gene subfamilies may have diverged from a single common ancestor prior to the mono-dicot split. Gene expression analysis based on RNA-seq data showed that three genes were expressed constitutively in all the tissues analyzed, implying that these genes might have specific function in pepper. Stress data analysis showed that the expression profiles of some members of the CaSTP gene family were altered under cold, heat, salt and hormone stress conditions. The present results will provide valuable information into the evolutionary relationships and functional divergence of the STP family in the future. ARTICLE HISTORY

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