The amino acid transporter AAP1 mediates growth and grain yield by regulating neutral amino acid uptake and reallocation in Oryza sativa

Abstract

Nitrogen (N) is a major element necessary for crop yield. In most plants, organic N is primarily transported in the form of amino acids. Here, we show that amino acid permease 1 (AAP1) functions as a positive regulator of growth and grain yield in rice. We found that the OsAAP1 gene is highly expressed in rice axillary buds, leaves, and young panicles, and that the OsAAP1 protein is localized to both the plasma membrane and the nuclear membrane. Compared with the wild-type ZH11, OsAAP1 overexpression (OE) lines exhibited increased filled grain numbers as a result of enhanced tillering, while RNAi and CRISPR (clustered regularly interspaced short palindromic repeat; Osaap1) knockout lines showed the opposite phenotype. In addition, OsAAP1-OE lines had higher concentrations of neutral and acidic amino acids, but lower concentrations of basic amino acids in the straw. An exogenous treatment with neutral amino acids promoted axillary bud outgrowth more strongly in the OE lines than in the WT, RNAi, or Osaap1 lines. Transcriptome analysis of Osaap1 further demonstrated that OsAAP1 may affect N transport and metabolism, and auxin, cytokinin, and strigolactone signaling in regulating rice tillering. Taken together, these results support that increasing neutral amino acid uptake and reallocation via OsAAP1 could improve growth and grain yield in rice.

The amino acid transporter OsAAP4 contributes to rice tillering and grain yield by regulating neutral amino acid allocation through two splicing variants

“…In rice, another organic nitrogen transporter of the NPF family, OsNPF7.3, transports di/tripeptides Gly-His and Gly-His-Gly (Ouyang et al 2010) and positively in uences rice tiller number and NUtE (Fang et al 2017). A recent study reveals that the amino acid transporter OsAAP1 mediates growth and grain yield by regulating neutral amino acid uptake and reallocation in rice (Ji et al 2020). Our study further indicated that as a result of arti cial selection, different rice accessions are able to adapt to the environment by regulating expression of different AATs.…”

“…Both variants of OsAAP4 might transport neutral amino acids to support rice tillering The protoplast-amino acid-FITC assay is a new method for examining plant amino acid transporters (Wang et al 2019a;Ji et al 2020). To further validate that OsAAP4 mediates Val and Pro transport, a protoplast amino acid-uptake assay was performed.…”

“…OsAAP3 mainly transports basic amino acids Lys and Arg (Taylor et al 2015), and recent studies demonstrated that blocking OsAAP3 or OsAAP5 expression increases grain yield by regulating the concentrations of these two amino acids (Lu et al 2018;Wang et al 2019a). Moreover, the amino acid transporter OsAAP1 mediate growth and grain yield by regulating neutral amino acid uptake and reallocation in rice (Ji et al 2020). In rice, in addition to OsAAPs, OsLHT1 has been shown to function in amino acid root uptake and source-to-sink allocation (Liu et al 2005;Wang et al 2019b;Guo et al 2020a;2020b).…”

The amino acid transporter OsAAP4 contributes to rice tillering and grain yield by regulating neutral amino acid transport through two splicing variants

“…Finally, tiller number is an important feature of the rice grain yield produced from bud initiation and elongation (Li et al 2003), and tiller bud outgrowth is regulated by both environmental signals and endogenous factors (Xing and Zhang 2010;Fang et al 2020). Of all the nitrogen transporters characterized to date, only OsNPF8.20, OsNPF6.5, OsNPF7.3, OsNPF7.2, OsNPF7.7, and OsAAP1 can positively regulate rice tiller number and enhance grain yield (Fang et al 2013;Hu et al 2015a;Fang et al 2017;Wang et al 2018;Huang et al 2018;Ji et al 2020). Our results indicated that overexpression of OsAAP4 also positively in uences tiller number by regulating expression of OsNPF6.5 and OsNPF7.7 (Fig.…”

“…OsAAP3 mainly transports basic amino acids Lys and Arg (Taylor et al 2015), and a recent study demonstrated that blocking OsAAP3 expression increases grain yield by regulating the concentrations of these two amino acids (Lu et al 2018). Moreover, the amino acid transporter OsAAP5 and OsAAP1 mediate growth and grain yield by regulating basic amino acid and neutral amino acid uptake and reallocation in rice (Wang et al 2019;Ji et al 2020). However, it is unclear whether other OsAAPs are also involved in rice growth and development.…”