GbLMI1 over-expressing improved cotton aboveground vegetative growth

Leaves are the main places for photosynthesis and organic synthesis of cotton. Leaf shape has important effects on the photosynthetic efficiency and canopy formation, thereby affecting cotton yield. Previous studies have shown that LMI1 is the main gene regulating leaf shape. In this study, the LMI1 gene (LATE MERISTEM IDENTITY1) was inserted into the 35S promoter expression vector, and cotton plants overexpressing LMI1(OE) were obtained through genetical transformation. Statistical analysis of the biological traits of T1 and T2 populations showed that compared to wild type (WT), OE plants had significant larger leaves, thicker stems and significantly increased dry weight. Furthermore, plant sections of the main vein and petiole showed that the number of cell in those tissues of OE plants increased significantly. In addition, RNA-seq analysis revealed differential expression of genes related to gibberellin synthesis and NAC gene family (genes containing the NAC domain) in OE and WT plants, suggesting that LMI1 is involved in secondary wall formation and cell proliferation, and promotes stem thickening. Moreover, GO (Gene Ontology) analysis enriched the terms of calcium ion binding, and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis enriched the terms of fatty acid degradation, phosphatidylinositol signal transduction system, and cAMP signal pathway. These results suggested that LMI1 OE plants were responsive to gibberellin hormone signals, and altered messenger signal (cAMP, Ca2+) which amplified this function, to promote the stronger above ground vegetative growth. This study found the LMI1 soared the nutrient growth in cotton, which is the basic for higher yield.