Dehydration stress influences the expression of brevis radix gene family members in sorghum (Sorghum bicolor)

Abstract

Brevis radix (BRX) constitutes a small gene family in angiosperms. It was first identified in Arabidopsis thaliana where it contributed to cell proliferation and root elongation. New roles of BRX family members in plant developmental processes and abiotic stress tolerance are getting revealed lately. In this study, we have identified six members belonging to the BRX gene family from Sorghum bicolor. Based on similarity analysis, two each of these members were found to be belonging to BRXL1 (Sobic.007G151500, Sobic.002G218600) and BRXL2 (Sobic.006G203200, Sobic.004G270100) classes and one was of BRXL4 (Sobic.001G008400) class. The sixth member (Sobic.006G117900) with a partial amino acid sequence was a pseudogene. All members except Sobic.006G117900 and Sobic.006G203200 had three conserved BRX domains. The number of exons of the members ranged from 3 to 6 and protein length from 313 to 469aa. All proteins had nuclear localization signals in them. Drought stress imposed on M35-1 genotype of sorghum for a duration of 7 days and 14 days brought about observable changes in root morphology. Mean root length per seedling significantly increased in the drought stressed seedlings. Expression analysis of sorghum BRX members using quantitative PCR showed enhanced expression of all members in drought stressed leaf as well as root tissues. While in leaves the expression of all BRX genes were up-regulated as duration of drought stress increased, only Sobic.007G151500 and Sobic.002G218600 showed enhanced expression in 14-day drought in the roots. Members of BRX gene family may be involved in drought tolerance in sorghum.