Identification of sugar transporter gene family <italic>SiSTPs</italic> in foxtail millet and its participation in stress response

Abstract

<p id="C3">Sugar transporter proteins (STPs), a class of monosaccharide transporters that mainly transport hexose, play an important role in the growth, development, and stress resistance of crops. Foxtail millet is the main cultivated crop in green dryland agriculture, and also is the model plant for C₄ photosynthesis mechanism and stress resistance gene mining of Gramineae crops. However, no systematical study of <italic>SiSTPs</italic> gene has been performed in foxtail millet. In this study, we identified the whole genome of six Gramineae crops including foxtail millet by bioinformatics method, and focused on the physicochemical properties, the chromosomal localization, the systematic evolution, gene structure, and the conserved domain. Moreover, the relative expression level of <italic>SiSTPs </italic>gene and its resistance to the infection of <italic>Sclerospora graminicola</italic> under drought stress and low phosphate stress in foxtail millet were investigated. The results showed that a total of 24, 26, 23, 22, 33, and 27 STP gene family members were individually identified in <italic>Setaria italica</italic>, <italic>Setaria viridis</italic>,<italic> Sorghum bicolor</italic>,<italic> Zea mays</italic>,<italic> Triticum aestivum</italic>, and <italic>Oryza sativa</italic>, which were divided into four clades by phylogenetic analysis. The 24 SiSTP genes were distributed unevenly on 7 chromosomes, and the size of the encoded amino acids ranged from 499 aa to 581 aa. The SiSTP all had the Sugar_tr (PF00083) conserved domain. The <italic>cis</italic>-acting elements included a large number of light-responsive elements and stress-responsive elements. These <italic>SiSTPs</italic> was subjected to strong purification and selection pressure during the evolutionary process of foxtail millet, and had obvious tissue expression specificity and photoinduced phenomena. Different <italic>SiSTPs</italic> showed different temporal and spatial expression and response to the drought stress, the low phosphate stress, and <italic>Sclerospora graminicola</italic> infection. Our results provide a theoretical basis for elucidating the function and response mechanism to stress of SiSTP.