Overexpression of ABA Receptor PYL10 Gene Confers Drought and Cold Tolerance to Indica Rice

Abstract

Abscisic acid (ABA) plays versatile functions in regulating plant development and tolerance to various biotic and abiotic stresses. Towards elucidating the functions of one of the ABA receptors (ABARs) in rice, <i>OsPYL10</i> was cloned from drought tolerant rice cv. Nagina 22 and was overexpressed under stress inducible <i>RD29A</i> promoter in a mega rice variety MTU1010 by using Agrobacterium mediated genetic transformation. Four single copy transgenic lines selected based on Southern blot analysis were used for physiological and molecular analysis. PYL10 receptor appears to regulate its ligand ABA accumulation as <i>PYL10</i> overexpressing transgenics accumulated 2-3.3-fold higher levels of ABA than that of WT in flag leaf at anthesis under non-stress conditions. The enhanced accumulation of ABA was associated with enhanced expression of genes for ABA biosynthesis viz., <i>ZEP1</i>, <i>NCED1</i>, <i>NCED2</i>, <i>NCED3</i>, and <i>NCED4</i> in transgenics than in WT plants. At seedling stage, <i>PYL10</i> transgenics showed significantly higher survival rate under cold stress as compared with WT plants. qRT-PCR analysis showed that expression levels of cold responsive genes viz., <i>DREB1F</i>, <i>MYB3R2</i>, <i>TPP1</i>, <i>COR410</i>, <i>DEHYDRIN</i>, <i>and LEA3</i> were significantly higher in PYL10 overexpressing transgenic lines as compared to WT plants under cold stress. <i>PYL10</i> transgenic and WT plants grown in the same pot were subjected to -80 kPa drought stress and recovery treatments at vegetative and reproductive stages. At vegetative stage drought stress, three overexpressing lines showed significantly higher grain yield (40-58%) and at reproductive stage drought stress one of these overexpression lines showed two-fold higher grain yield than that of WT plants. Excised leaf water loss analysis showed that <i>PYL10</i> transgenic lost about 20% less water than WT plants. At reproductive stage, <i>OsPYL10</i> transgenic maintained higher RWC, membrane stability index, chlorophyll content, and accumulated lower amount of MDA and H₂O₂ as compared with WT plants. qRT-PCR analysis showed that expression levels of <i>RAB16</i>, <i>Dehydrin</i>, <i>LEA3</i>, and <i>ABA45</i> were higher in <i>PYL10</i> transgenics as compared with WT plants under drought stress. Thus, overall results showed that <i>OsPYL10</i> overexpression has potential to improve both drought and cold stress tolerance of indica rice.