Water relation and aquaporin genes (PIP1;2 and PIP2;1) expression at the reproductive stage of rice (Oryza sativa L. spp. indica) mutant subjected to water deficit stress

Rice (Oryza sativa L. spp. indica) is a carbohydrate crop that grows well in the aquatic habitat. In the drought prone areas, adaptive growth ability and plant defence mechanisms coping with less water are challenging tasks for rice breeder to maintain rice productivity. Rice plants, including Thai jasmine rice (cv. KDML105; wild type), M401 mutant line derived from KDML105 (upon treatment with EMS and gamma-irradiation), and Pathumthani 1 (PT1, a negative check -drought susceptible), were grown in the pot culture until booting stage (inflorescence formation) and then subjected to water withholding for 14 days (water deficit stress) represented by 5.28% soil water content (SWC) and well watering (control; 31.9% SWC). Water use efficiency (WUE), net photosynthetic rate (P-n), transpiration rate (E), stomatal conductance (g(s)) and expression of PIP1; 2 and PIP2; 1 were examined in flag leaf tissues of rice grown under control and water deficit stress. WUE in MT401 mutant plant subjected to water deficit stress was increased, whereas P-n in both MT401 and KDML105 was maintained. Transcriptional levels of OsPIP1; 2 and OsPIP2; 1 in the MT401 grown under water deficit stress were up-regulated by 2.0-2.5 folds higher than those in KDML105 and PT1 genotype. The expression of OsPIP2; 1 in MT401 mutant plant was maintained when plants were exposed to water deficit condition, resulting in stabilization of WUE at the cellular levels. In addition, panicle length and number of spikelets per panicle in MT401 mutant were retained well under water deficit, suggesting MT401 as water deficit tolerant type.