Drought tolerant gene identification by rice genome comparison and gene characterization in arabidopsis plant model

Abstract

Abiotic stresses, especially drought and salt stresses can affect plant growth and productivity. ‘Kao Dawk Mali 105’ (‘KDML105’) rice is one of the crops which has to face both drought and salt stresses as it is grown in rain-fed saline soil in the northeastern region of Thailand, where the irrigation is limited. CSSL104, a chromosome substitution line with ‘KDML105’ genetic background, was developed in order to improve drought tolerant ability of ‘KDML105’ rice by transferring the drought tolerant (DT)-QTL region from double haploid line, DH103. Photosynthesis parameters of CSSL104 and its parental lines, ‘KDML105’ and DH103, were investigated, when they were grown in normal and drought-stress conditions. Net photosynthesis rates of all lines were similar in normal condition. In drought stress, net photosynthesis rate of all lines was declined, but CSSL104 and DH103 rice had the significant higher photosynthetic rate than ‘KDML105’ rice under drought-stressed condition. Based on the SNPs comparison between CSSL104 and ‘KDML105’ rice and gene co-expression network analysis, nine genes were involved in photosynthesis and six genes from those genes were used to study in Arabidopsis mutant lines containing the mutation in the homologous genes of the predicted ones. The mutant lines containing the mutation in LOC_Os01g72950, LOC_Os07g37550, LOC_Os07g38300, and LOC_Os10g10170 showed better growth than wild type (WT) under drought stress. The expression of LOC_Os07g37550 and LOC_Os08g41460 in ‘KDML105’ was higher than the expression in CSSL104 and DH103 under drought stress. It supported the result of net photosynthesis that ‘KDML105’ was more susceptible to drought stress than CSSL104 and DH103. Therefore, it was proposed that these genes were involved in drought tolerant mechanism in CSSL104.

The predicted drought tolerance genes from CSSL104, Ndh-O, Lhcb3, Rrf, Pgrl5-like, LOC_Os09g39390, Mrl1, together with LOC_Os01g68450, the predicted salt tolerance gene from CSSL16 were evaluated for salt tolerance involvement by using the Arabidopsis mutant lines containing the mutation in the homologous genes of the predicted ones. At1g65230 is orthologous to LOC_Os01g68450 gene in rice and at1g65230 Arabidopsis mutant performed the highest growth inhibition under salt stress condition when compared to other mutant lines. The revertant and ectopic expression lines with LOC_Os01g68450 gene show the higher growth parameters than the at1g65230 mutant under drought and salt stress. Moreover, the ectopic expression lines showed high net photosynthesis and pigments content under salt stress. These suggested that LOC_Os01g68450 gene has a function to maintain pigments contents under drought and salt stress leading to the photosynthesis adaptation during drought and salt stress.