New Phytol|南京农大资环学院张亚丽研究团队揭示OsPIN9蛋白是铵调节水稻分蘖芽生长所必需的。
水稻分蘖程度是一个重要的农艺性状，氮素供应对其有显着影响。然而，关于氮素调控的水稻分蘖与生长素极性运输之间的关系还知之甚少。
与硝酸盐相比，铵态氮促进了分蘖的发育，并与~3H-吲哚乙酸(IAA)运输增加和生长素进入结合部的增加相平行。根据基因芯片数据，选择生长素分泌载体OsPIN9作为铵调控分蘖的候选基因。与野生型植株相比，ospin9突变体的分蘖数较少，OsPIN9过表达增加了分蘖数。
此外，OsPIN9主要在分蘖芽和结合部的维管组织中表达，并编码一种膜定位蛋白。在非洲爪蟾卵母细胞和酵母中的异源表达表明OsPIN9是一种功能性生长素外排转运蛋白。
更重要的是，它的RNA和蛋白质水平是由铵诱导的，而不是由硝酸盐诱导的，并且突变体中的分蘖数对氮素形态没有反应。
与高施氮量相比，低施氮量稻田中的高表达品系具有更多的优势，包括增加分蘖数和籽粒产量。
我们的数据显示，铵供应和生长素外流转运体协同控制水稻分蘖芽的伸长。
The degree of rice tillering is an important agronomic trait that can be markedly affected by nitrogen supply. However, less is known about how nitrogen‐regulated rice tillering is related to polar auxin transport. Compared with nitrate, ammonium induced tiller development and was paralleled with increased 3H‐indole‐acetic acid (IAA) transport and greater auxin into the junctions. OsPIN9, an auxin efflux carrier, was selected as the candidate gene involved in ammonium‐regulated tillering based on GeneChip data. Compared with wild‐type plants, ospin9 mutants had fewer tillers, and OsPIN9 overexpression increased the tiller number. Additionally, OsPIN9 was mainly expressed in vascular tissue of the junction and tiller buds, and encoded a membrane‐localised protein. Heterologous expression in Xenopus oocytes and yeast demonstrated that OsPIN9 is a functional auxin efflux transporter. More importantly, its RNA and protein levels were induced by ammonium but not by nitrate, and tiller numbers in mutants did not respond to nitrogen forms. Further advantages, including increased tiller number and grain yield, were observed in overexpression lines grown in the paddy field at a low‐nitrogen rate compared with at a high‐nitrogen rate. Our data revealed that ammonium supply and an auxin efflux transporter co‐ordinately control tiller bud elongation in rice.
Hou, M., Luo, F., Wu, D., Zhang, X., Lou, M., Shen, D., Yan, M., Mao, C., Fan, X., Xu, G. and Zhang, Y. (2020), OsPIN9, an auxin efflux carrier, is required for the regulation of rice tiller bud outgrowth by ammonium. New Phytol. doi:10.1111/nph.16901
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