Hubei Engineering Research Center of Viral Vector, Wuhan University of Bioengineering, Wuhan 430415, China.
Hubei Engineering Research Center of Viral Vector, Wuhan University of Bioengineering, Wuhan 430415, China; National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
Plant Sci. 2019 Jun;283:23-31. doi: 10.1016/j.plantsci.2019.01.019. Epub 2019 Feb 26.
The rice nitrate and di/tripeptide transporter (NPF) gene family plays an indispensable role in nitrogen transport and plant growth. In this study, 18 alternatively spliced OsNPF genes with 36 different forms of mRNAs were identified, and two of these, namely OsNPF7.1 and OsNPF7.4, showed opposite expression patterns in axillary buds under different nitrogen concentrations. Our results indicate that the expression levels of OsNPF7.1 and OsNPF7.4 determine the axillary bud outgrowth, especially for the second bud, and subsequently influence the tiller number in rice. The overexpression of either of the variants of OsNPF7.1 or the knockout of OsNPF7.4 increased the seedling biomass as well as the tiller number, filled grain number, and grain yield in rice. However, the RNAi-mediated silencing of OsNPF7.1 or the overexpression of either of the variants of OsNPF7.4 had an opposite effect. The overexpression of OsNPF7.1 or OsNPF7.4 could improve the uptake of nitrate, but the OsNPF7.4-overexpressing plants had lower biomass. It is possible that excessive nitrate in the OsNPF7.4-overexpressing plants led to the accumulation of amino acids in the leaf sheath, which inhibited seedling biomass. In addition, the reduced reutilization of nitrate in the seedlings also limited the plant biomass. However, the moderate increase in nitrate and amino acid concentrations in the OsNPF7.1-overexpressing plants could promote seedling biomass and enhance grain yield. In conclusion, our data suggest that different members in the NPF family have different roles in rice, and this study suggests an alternative way to modify rice architecture and enhance grain yield by regulating the expression of OsNPF7.1 and OsNPF7.4.
水稻硝酸盐和二/三肽转运体（NPF）基因家族在氮素转运和植物生长中起着不可或缺的作用。在这项研究中，鉴定出了 18 个具有 36 种不同形式 mRNA 的水稻 NPF 基因的选择性剪接体，其中两个基因，即 OsNPF7.1 和 OsNPF7.4，在不同氮浓度下的腋芽中表现出相反的表达模式。我们的结果表明，OsNPF7.1 和 OsNPF7.4 的表达水平决定了腋芽的生长，特别是第二个芽，从而影响水稻的分蘖数。OsNPF7.1 变体的过表达或 OsNPF7.4 的敲除均增加了水稻幼苗生物量以及分蘖数、充实粒数和产量。然而，OsNPF7.1 的 RNAi 介导的沉默或 OsNPF7.4 变体的过表达则产生了相反的效果。OsNPF7.1 的过表达或 OsNPF7.4 变体的过表达均能改善硝酸盐的摄取，但 OsNPF7.4 过表达植株的生物量较低。这可能是因为 OsNPF7.4 过表达植株中过量的硝酸盐导致叶鞘中氨基酸的积累，从而抑制了幼苗的生物量。此外，幼苗中硝酸盐的再利用减少也限制了植株的生物量。然而，OsNPF7.1 过表达植株中硝酸盐和氨基酸浓度的适度增加可以促进幼苗生物量并提高产量。总之，我们的数据表明，NPF 家族的不同成员在水稻中具有不同的作用，本研究提出了一种通过调节 OsNPF7.1 和 OsNPF7.4 的表达来改变水稻结构和提高产量的替代方法。
