High Overexpression of Leads to Growth Inhibition and Protein Ectopic Localization in Transgenic .

Amino acid permeases (AAPs) transporters are crucial for the long-distance transport of amino acids in plants, from source to sink. While and rice have been extensively studied, research on foxtail millet is limited. This study identified two transcripts of , both of which were induced by NO and showed similar expression patterns. The overexpression of and in inhibited plant growth and seed size, although SiAAP9 was found to transport more amino acids into seeds. Furthermore, transgenic showed increased tolerance to high concentrations of glutamate (Glu) and histidine (His). The high overexpression level of suggested its protein was not only located on the plasma membrane but potentially on other organelles, as well. Interestingly, sequence deletion reduced SiAAP9's sensitivity to Brefeldin A (BFA), and SiAAP9 had ectopic localization on the endoplasmic reticulum (ER). Protoplast amino acid uptake experiments indicated that SiAAP9 enhanced Glu transport into foxtail millet cells. Overall, the two transcripts of have similar functions, but SiAAP9L shows a higher colocalization with BFA compartments compared to SiAAP9S. Our research identifies a potential candidate gene for enhancing the nutritional quality of foxtail millet through breeding.