Overexpression of a DEAD box helicase, PDH45, confers both seedling and reproductive stage salinity tolerance to rice (Oryza sativa L.)

Abstract

To improve the salinity tolerance of rice, a DEAD-box helicase gene isolated from pea with a CaMV35S promoter was transformed into the Bangladeshi rice variety Binnatoa through Agrobacterium-mediated transformation. The transgenic seedlings showed significantly higher chlorophyll content, but decreased root length compared to wild type (WT) under normal physiological conditions. Their status was confirmed by polymerase chain reaction (PCR), semi-quantitative reverse-transcription PCR and Southern blot hybridization for positive integration of the transgene. The T2 progenies from three independent transformation events were characterized for salinity tolerance both at seedling and reproductive stages. Compared to the WT plants, the average decrease in chlorophyll content and dry weight of seedling leaves was lower by 20 and 12% respectively at 12 deciSiemens per meter (dS/m) NaCl stress in hydroponics. A higher leaf K⁺/Na⁺ ratio of 0.346 was maintained by the transgenic lines compared to the WT ratio of 0.157, which indicated induced ion homeostasis. At the reproductive stage, transgenic rice plants expressing PDH45 showed better fertility and produced higher grain yield by 16% compared to WT plants under continuous stress of 6 dS/m from 30 days till maturity. One of the transformed lines, PDH45-P3, outperformed the others, and replicated data in reproductive stage soil stress of 12 dS/m NaCl showed its enhanced fertility and yield by 46 and 29% over WT, respectively.