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The plant PTR/ NRT1 (peptide transporter/nitrate transporter 1) gene family comprises di/tripeptide and low-affinity nitrate transporters; some members also recognize other substrates such as carboxylates, phytohormones (auxin and abscisic acid), or defence compounds (glucosinolates). Little is known about the members of this gene family in rice ( Oryza sativa L.). Here, we report the influence of altered Os PTR9 expression on nitrogen utilization efficiency, growth, and grain yield. Os PTR9 expression is regulated by exogenous nitrogen and by the day-night cycle. Elevated expression of Os PTR9 in transgenic rice plants resulted in enhanced ammonium uptake, promotion of lateral root formation and increased grain yield. On the other hand, down-regulation of Os PTR9 in a T- DNA insertion line ( osptr9) and in Os PTR9- RNAi rice plants had the opposite effect. These results suggest that Os PTR9 might hold potential for improving nitrogen utilization efficiency and grain yield in rice breeding. [ABSTRACT FROM AUTHOR]

Background: Rice tiller number is one of the most important factors that determine grain yield, while nitrogen is essential for the crop growth and development, especially for tiller formation. Genes involved in nitrogen use efficiency processes have been identified in the previous studies, however, only a small number of these genes have been found to improve grain yield by promoting tillering.Results: We constructed over-expression (OX) lines and RNA-interference (Ri) lines, and selected a mutant of OsNPF7.2, a low-affinity nitrate transporter. Our analyses showed that rice tiller number and grain yield were significantly increased in OX lines, whereas Ri lines and mutant osnpf7.2 had fewer tiller number and lower grain yield. Under different nitrate concentrations, tiller buds grew faster in OX lines than in WT, but they grew slower in Ri lines and mutant osnpf7.2. These results indicated that altered expression of OsNPF7.2 plays a significant role in the control of tiller bud growth and regulation of tillering. Elevated expression of OsNPF7.2 also improved root length, root number, fresh weight, and dry weight. However, reduced expression of OsNPF7.2 had the opposite result on these characters. OsNPF7.2 OX lines showed more significantly enhanced influx of nitrate and had a higher nitrate concentration than WT. The levels of gene transcripts related to cytokinin pathway and cell cycle in tiller bud, and cytokinins concentration in tiller basal portion were higher in OX lines than that in WT, suggesting that altered expression of OsNPF7.2 controlled tiller bud growth and root development by regulating cytokinins content and cell cycle in plant cells. Altered expression of OsNPF7.2 also was responsible for the change in expression of the genes involved in strigolactone pathway, such as D27, D17, D10, Os900, Os1400, D14, D3, and OsFC1.Conclusion: Our results suggested that OsNPF7.2 is a positive regulator of nitrate influx and concentration, and that it also regulates cell division in tiller bud and alters expression of genes involved in cytokinin and strigolactone pathways, resulting in the control over rice tiller number. Since elevated expression of OsNPF7.2 is capable of improving rice grain yield, this gene might be applied to high-yield rice breeding. [ABSTRACT FROM AUTHOR]

Amino acid transporters play important roles in plant growth and stress tolerance; however, whether the abscisic acid signaling pathway regulates their transcription in rice (Oryza sativa) under salt stress remains unclear. In this study, we report that the transcription factor OsMYB2 (MYB transcription factor 2) of the abscisic acid signaling pathway mediates the expression of the gene encoding the amino acid transporter OsANT1 (aromatic and neutral amino acid transporter 1), which positively regulates growth and salt tolerance in rice. OsANT1 was mainly expressed in the leaf blade and panicle under normal conditions and transports leucine, phenylalanine, tyrosine and proline, positively regulating tillering and yield in rice. Nevertheless, salt stress induced the accumulation of abscisic acid and strongly increased the expression level of OsANT1 in the root, resulting in enhanced salt tolerance of rice seedlings, as evidenced by higher proline concentration and antioxidant-like enzyme activities and lower malondialdehyde and hydrogen peroxide concentrations. Moreover, we showed that OsMYB2 interacts with the promoter of OsANT1 and promotes its expression. Overexpression of OsMYB2 also improved tillering, yield, and salt tolerance in rice. In conclusion, our results suggest that the transcription factor OsMYB2 triggers OsANT1 expression and regulates growth and salt tolerance in rice, providing insights into the role of the abscisic acid signaling pathway in the regulatory mechanism of amino acid transporters in response to salt stress., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Kam Sweet Rice is a high-quality local variety of Guizhou province in China, but most varieties have awns on lemma. In this study, we aimed to obtain awnless varieties of Kam Sweet Rice by blocking the awn development-related gene OsGAD1 using CRISPR/Cas9 technology. We determined that natural variations of the OsGAD1 triggered different lengths of awns of Kam Sweet Rice. We found that the awning rate of the CRISPR lines of OsGAD1 in Guxiangnuo, Goujingao and Gouhuanggang decreased by over 65%, and the number of grains per panicle and yield per plant increased by more than 17% and 20% compared to the wild-types. Furthermore, we indicated that blocking OsGAD1 resulted in an increase of over 2% in the brown rice rate and milled rice rate in these varieties. In addition, the analysis of the transcriptome revealed that the regulation of awn development and yield formation in CRISPR lines of OsGAD1 may involve genes associated with phytohormone and nitrogen pathways. These results suggest that blocking OsGAD1 in Kam Sweet Rice using CRISPR/Cas9 technology can be used for breeding programs seeking high yield and grain quality of Kam Sweet Rice., (© 2024 Scandinavian Plant Physiology Society.)