Aquaporin plays an important role in mediating chloroplastic CO2 concentration under high‐N supply in rice (Oryza sativa) plants
2016
Ding, Lei | Gao, Limin | Liu, Wei | Wang, Min | Gu, Mian | Ren, Binbin | Xu, Guohua | Shen, Qirong | Guo, Shiwei
Our previous studies demonstrated that chloroplastic CO₂ concentration (Cc) is not sufficient under high‐nitrogen (N) supply in rice plants. In this research, we studied how aquaporins‐ (AQPs) mediated Cc under different N‐supply levels. A hydroponic experiment was conducted in a greenhouse with three different N levels (low N, 0.71 mM; intermediate N, 2.86 mM; and high N, 7.14 mM) in a rice cultivar (Oryza sativa cv. Shanyou 63) and with an ospip1;1 mutant (Oryza sativa cv. Nipponbare). The photosynthetic nitrogen‐use efficiency (PNUE) decreased with increasing leaf‐N content. Under high‐N supply, the estimated Cc was significantly lower than the theoretical Cc and the specific Rubisco activity (carboxylation efficiency/Rubisco content, CE/Rubisco) decreased, because of a decrease of relative CO₂ diffusion conductance (total CO₂ diffusion conductance/leaf‐N content, gₜ/N) in mesophyll cells. Real Time Quantitative PCR (Q‐RT‐PCR) showed that most OsPIP1s and OsPIP2s expression were downregulated under the high‐N supply. Furthermore, Cc and gₘ decreased in the ospip1;1 mutant line compared with that of the wild‐type plant. It was concluded that under high‐N supply, the decreased PNUE was associated with non‐sufficient Cc, mediated by AQP in mesophyll conductance.
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