Zhong Sihui, Mahmood Kashif, Bi Yong-Mei, Rothstein Steven J, Ranathunge Kosala
Department of Molecular and Cellular Biology, University of Guelph, GuelphON, Canada.
London Research and Development Centre, Agriculture and Agri-Food Canada, LondonON, Canada.
Front Plant Sci. 2017 Jun 2;8:928. doi: 10.3389/fpls.2017.00928. eCollection 2017.
Current agricultural practices rely on heavy use of fertilizers for increased crop productivity. However, the problems associated with heavy fertilizer use, such as high cost and environmental pollution, require the development of crop species with increased nutrient use efficiency. In this study, by using transgenic approaches, we have revealed the critical role of OsNLA1 in phosphate (Pi) accumulation of rice plants. When grown under sufficient Pi and nitrate levels, OsNLA1 knockdown (, and ) lines accumulated higher Pi content in their shoot tissues compared to wild-type, whereas, over-expression lines (OsNLA1-OE1, OsNLA1-OE2, and OsNLA1-OE3) accumulated the least levels of Pi. However, under high Pi levels, knockdown lines accumulated much higher Pi content compared to wild-type and exhibited Pi toxicity symptoms in the leaves. In contrast, the over-expression lines had 50-60% of the Pi content of wild-type and did not show such symptoms. When grown under limiting nitrate levels, OsNLA1 transgenic lines also displayed a similar pattern in Pi accumulation and Pi toxicity symptoms compared to wild-type suggesting an existence of cross-talk between nitrogen (N) and phosphorous (P), which is regulated by OsNLA1. The greater Pi accumulation in knockdown lines was a result of enhanced Pi uptake/permeability of roots compared to the wild-type. The cross-talk between N and P was found to be nitrate specific since the knockdown lines failed to over-accumulate Pi under low (sub-optimal) ammonium level. Moreover, OsNLA1 was also found to interact with OsPHO2, a known regulator of Pi homeostasis, in a Yeast Two-Hybrid (Y2H) assay. Taken together, these results show that OsNLA1 is involved in Pi homeostasis regulating Pi uptake and accumulation in rice plants and may provide an opportunity to enhance P use efficiency by manipulating nitrate supply in the soil.
当前的农业生产方式依赖大量使用化肥来提高作物产量。然而，与大量使用化肥相关的问题，如高成本和环境污染，需要培育养分利用效率更高的作物品种。在本研究中，我们通过转基因方法揭示了OsNLA1在水稻植株磷（Pi）积累中的关键作用。在充足的Pi和硝酸盐水平下生长时，与野生型相比，OsNLA1基因敲低（ ，以及 ）品系地上组织中积累了更高的Pi含量，而过量表达品系（OsNLA1-OE1、OsNLA1-OE2和OsNLA1-OE3）积累的Pi水平最低。然而，在高Pi水平下，基因敲低品系积累的Pi含量比野生型高得多，并且在叶片中表现出Pi毒性症状。相比之下，过量表达品系的Pi含量是野生型的50-60%，且未表现出此类症状。在硝酸盐水平受限的条件下生长时，与野生型相比，OsNLA1转基因品系在Pi积累和Pi毒性症状方面也表现出类似模式，这表明氮（N）和磷（P）之间存在相互作用，且受OsNLA1调控。与野生型相比，基因敲低品系中更高的Pi积累是根系对Pi吸收/通透性增强的结果。发现N和P之间的相互作用具有硝酸盐特异性，因为在低（次优）铵水平下，基因敲低品系未能过度积累Pi。此外，在酵母双杂交（Y2H）试验中还发现OsNLA1与已知的Pi稳态调节因子OsPHO2相互作用。综上所述，这些结果表明OsNLA1参与水稻植株的Pi稳态调节Pi吸收和积累，并且可能通过控制土壤中的硝酸盐供应提供提高磷利用效率的机会。
