Background

Amino acids, which are transported by amino acid transporters, are the major forms of organic nitrogen utilized by higher plants. Among the 19 Amino Acid Permease transporters (AAPs) in rice, only a small number of these genes have been reported to influence rice growth and development. However, whether other OsAAPs are responsible for rice growth and development is unclear.

Results

In this study, we demonstrate that OsAAP4 promoter sequences are divergent between Indica and Japonica, with higher expression in the former, which produces more tillers and higher grain yield than does Japonica. Overexpression of two different splicing variants of OsAAP4 in Japonica ZH11 significantly increased rice tillering and grain yield as result of enhancing the neutral amino acid concentrations of Val, Pro, Thr and Leu. OsAAP4 RNA interference (RNAi) and mutant lines displayed opposite trends compared with overexpresing (OE) lines. In addition, exogenous Val or Pro at 0.5 mM significantly promoted the bud outgrowth of lines overexpressing an OsAAP4a splicing variant compared with ZH11, and exogenous Val or Pro at 2.0 mM significantly enhanced the bud outgrowth of lines overexpressing splicing variant OsAAP4b compared with ZH11. Of note, the results of a protoplast amino acid-uptake assay showed that Val or Pro at different concentrations was specifically transported and accumulated in these overexpressing lines. Transcriptome analysis further demonstrated that OsAAP4 may affect nitrogen transport and metabolism, and auxin, cytokinin signaling in regulating rice tillering.

Conclusion

Our results suggested that OsAAP4 contributes to rice tiller and grain yield by regulating neutral amino acid allocation through two different splicing variants and that OsAAP4 might have potential applications in rice breeding.

中文翻译：

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氨基酸转运蛋白OsAAP4通过两个剪接变异体调节中性氨基酸分配，从而促进了水稻分iller和籽粒产量。

背景

由氨基酸转运蛋白转运的氨基酸是高等植物利用的有机氮的主要形式。在水稻中的19种氨基酸通透酶转运蛋白（AAP）中，只有少数这些基因影响水稻的生长发育。但是，尚不清楚其他OsAAP是否对水稻的生长和发育负责。

结果

在这项研究中，我们表明，OsAAP4启动子序列可之间发散籼稻和粳稻，与前更高的表达，这产生更多的分蘖和更高的产量比不粳稻。由于提高了Val，Pro，Thr和Leu的中性氨基酸浓度，在粳稻ZH11中OsAAP4的两个不同剪接变体的过表达显着提高了水稻分till和谷物产量。与过度表达（OE）系相比，OsAAP4 RNA干扰（RNAi）和突变系显示相反的趋势。此外，0.5 mM的外源Val或Pro显着促进了过表达FPS的品系的芽生长。与ZH11相比，OsAAP4a剪接变体以及2.0 mM的外源Val或Pro显着增强了与ZH11相比过表达剪接变体OsAAP4b的品系的芽生长。值得注意的是，原生质体氨基酸摄取测定的结果表明，在这些过表达细胞系中，不同浓度的Val或Pro被特异性转运和积累。转录组分析进一步证明，OsAAP4可能影响氮的转运和代谢以及生长素，细胞分裂素的信号传导，从而调节水稻分ing。

结论

我们的结果表明，OsAAP4通过调节两个不同的剪接变体来调节中性氨基酸的分配，从而有助于水稻分till和谷物产量，并且OsAAP4可能在水稻育种中具有潜在的应用。