GbLMI1 over-expression improves cotton aboveground vegetative growth

Abstract

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

Keywords

• LMI1
• over-expressing
• cotton
• vegetative growth