Overexpression of the Autophagy-Related Gene Siatg8a from Foxtail Millet (Setaria Italica L.) in Transgenic Wheat Confers Tolerance to Phosphorus Starvation

Abstract

In plants, autophagy plays an important role in regulating intracellular degradation and amino acid recycling in response to nutrient starvation, senescence, and other environmental stresses. Foxtail millet (Setaria italica) shows strong resistance to various abiotic stresses; however, current understanding of the regulation network of abiotic stress resistance in foxtail millet remains limited. In this study, we aimed to determine the autophagy-related gene SiATG8a in tissues of foxtail millet. We found that SiATG8a was mainly expressed in the stem and was induced by low-phosphorus (LP) stress. Overexpression of SiATG8a in wheat (Triticum aestivum) significantly increased the grain yield and spike number per m2 under LP treatment compared to those in the WT varieties S366 and S4056. There was no significant difference in the grains P content between SiATG8a-overexpressing wheat and WT wheat under normal phosphorus (NP) treatment. However, the phosphorus content in the roots, stems, and leaves of transgenic plants was significantly higher than that in WT plants under NP and LP conditions. Furthermore, the expression of P transporter genes, such as TaPHR1, TaPHR3, TaIPS1, and TaPT9, in SiATG8a-transgenic wheat was higher than that in WT under LP. Collectively, overexpression of SiATG8a increased the grain yield of transgenic wheat plants under LP by affecting the expression of phosphorus-related transporter genes; thus, SiATG8a could be a candidate gene in transgenic wheat for improving tolerance to LP stress in the field.

Keywords: Autophagy-associated genes, Foxtail millet (Setaria italica), Grain yield, Low-phosphorus stress, Transgenic wheat.