Genome-wide identification and functional analysis of the SiCIN gene family in foxtail millet (Setaria italica L.)

Cell wall invertase (CIN) is a vital member of plant invertase (INV) and plays a key role in the breakdown of sucrose. This enzyme facilitates the hydrolysis of sucrose into glucose and fructose, which is crucial for various aspects of plant growth and development. However, the function of CIN genes in foxtail millet (Setaria italica) is less studied. In this research, we used the blast-p of NCBI and TBtools for bidirectional comparison, and a total of 13 CIN genes (named SiCINs) were identified from foxtail millet by using Arabidopsis and rice CIN sequences as reference sequences. The phylogenetic tree analysis revealed that the CIN genes can be categorized into three subfamilies: group 1, group 2, and group 3. Furthermore, upon conducting chromosomal localization analysis, it was observed that the 13 SiCINs were distributed unevenly across five chromosomes. Cis-acting elements of SiCIN genes can be classified into three categories: plant growth and development, stress response, and hormone response. The largest number of cis-acting elements were those related to light response (G-box) and the cis-acting elements related to seed-specific regulation (RY-element). qRT-PCR analysis further confirmed that the expression of SiCIN7 and SiCIN8 in the grain was higher than that in any other tissues. The overexpression of SiCIN7 in Arabidopsis improved the grain size and thousand-grain weight, suggesting that SiCIN7 could positively regulate grain development. Our findings will help to further understand the grain-filling mechanism of SiCIN and elucidate the biological mechanism underlying the grain development of SiCIN.