Genomic approaches to dissect drought tolerance in Castanea sativa

Drought stress, intensified by climate change, could significantly impact the Mediterranean region affecting European chestnut (Castanea sativa). Unfortunately, no in-depth research has been carried out to identify and characterise drought tolerance genes in the genus Castanea, especially in C. sativa, whose genome remains unpublished. This study is based on the knowledge of drought tolerance in Quercus spp. taking advantage of the high genomic synteny with Castanea spp. that allows the transfer of genomic and trait information. Our main objectives are to obtain the sequences of candidate genes involved in drought tolerance in C. sativa and to examine the degree of cross-species conservation using bioinformatic tools. A total of 26 candidate genes were selected based on GO terms from a transcriptome study in Quercus spp. NCBI BLASTp search revealed the orthologous in C. mollissima and C. crenata for most of the genes. A consensus sequence was obtained for each gene by aligning the sequences of C. mollissima and C. crenata to query a C. sativa sequence read archive database (SRA, NCBI). The putative sequences of candidate genes in C. sativa were obtained by mapping short sequence reads. Both alignment and mapping procedures showed a high degree of coverage and identity. These results seem to confirm the high conservation within Quercus and Castanea genera and among chestnut species. However, there are four genes with mapping coverage below 60% and three genes found only in one Castanea species that appear to be less conserved. These seven genes are significant for future research as they could elucidate variations in drought tolerance. Overall, the study workflow successfully obtained gene sequences related to drought tolerance in C. sativa with a high level of confidence. The obtained putative gene sequences are valuable for developing molecular markers and conducting gene expression profile studies.