Functional study of certain genes selected from SSH library of common bean under salinity stress

Abstract

Considering that one third of Earth’s arable lands are affected by soil salinity, understanding how plants respond to salinity stress and creation of stress tolerant crops is of outmost importance. Phaseolus vulgaris (common bean) is a major legume crop produced extensively around the world and in Turkey, but it is also one of the most salt susceptible crops. We aimed to functionally characterize candidate genes selected from subtractive cDNA libraries enriched in salt responsive genes and also from previous studies on candidate genes that are reported to confer enhanced tolerance upon overex-pression. Seven candidate genes from the SSH library and eleven candidate genes from literature were selected. Seven candidate genes from literature and three candidate genes from the SSH library were confirmed to be differentially expressed at a signifi-cant level in leaf tissues of Ispir and TR43477 varieties upon salt treatment. Three can-didate genes from literature, Na+-H+ antiporter (NHX), superoxide dismutase (SOD), and plasma membrane integral protein (PIP) together with one gene from the SSH li-brary, vacuolar H+-ATPase (pvVHP) were cloned from common bean and constitutive-ly overexpressed in wild type (Col-0) Arabidopsis thaliana lines following floral dip transformation. Furthermore, T-DNA insertional knock out lines for predicted Ara-bidopsis orthologs were also transformed with the same four candidate genes (pvNHX, pvSOD, pvPIP and pvVHP). Salt stress treatments of knock out lines afor all four of the candidate genes and overexpression lines for NHX, SOD, and VHP have not revealed any phenotypic difference in salinity tolerance compared to wild type. However, two independent PIP overexpression lines (PIP412-8 and PIP412-10) have shown signifi-cantly greater fresh weight and leaf area only under control conditions but under none of the treatment conditions. Further experiments such as creation of overexpression lines with confirmed overexpression at the protein level and quantitative comparison of overexpressed transcript levels with respect to native orthologues are needed to draw firmer conclusions for functional effects of the analyzed candidate genes.