Structural and functional analysis of two sHSP subfamilies in tomato ripening

Abstract

The small Heat Shock Proteins (sHSP) gene family shows a high copy number of members, involved in stress and developmental processes in plants. We have studied the genomic structure and function of two sHSP subfamilies on chromosomes 6 and 9 in Solanum lycopersicum cv. Caimanta and S. pimpinellifolium accession LA0722, which are the parental lines of different breeding populations obtained by our research group. A similar tandem genomic arrangement between cv. Caimanta and accession LA0722, compared to the reference tomato genome cv Heinz 1706, has been observed, with 4 and 2 members, respectively. Gene variations having a copy number from 3 to 5 members for these sHSP, were identified in representative exotic tomato species (S. pennelli LA0716 and S. habrochaites LYC4) and the related crop potato. In order to obtain a better understanding of the regulation of both sHSP groups in fruit ripening, transcriptome analysis by RNA-Seq was performed. Differences in gene expression among cv. Caimanta and accession LA0722 were identified, and previously detected interactors were actively expressed for both sHSP clusters. Promoter regions of these sHSP and their interactors had molecular polymorphism with variation on HSE densities. Our results can be used in breeding programs for the design of sequence-based specific molecular markers, enabling a more efficient development of new commercial varieties with desired traits related to sHSP differential expression.