Sucrose Synthase Genes Showed Genotype-Dependent Expression in Sugarcane Leaves in the Early Stage of Growth

Sucrose synthase (SuSy) is one of the key enzymes regulating sucrose metabolism in plants. There are at least five different SuSy genesexist in sugarcane, and their biological functions are not fully understood. In this paper, the phylogenetic analysis of all plantSuSygenes published to-date (109) has been grouped into three classes: SuSyI, SuSyII and SuSyIII. SuSyIwas further divided into monocot and eudicot SuSyI, indicating their independent evolutionary trajectory paralleling monocot and dicot divergence. The leaf total sugar content of high-, medium-and low-sugar sugarcane genotypes varied at the early stage of plant growth. However, there was no strong correlation between early-stage leaf sucrose content and the final stem sugar content and sugar yield of mature crop. The proportion of leaf sucrose and fructose content in most sugarcane genotypes in the early stage of growth was about 30%each, and that of glucose was about 40%. The SuSy enzyme activity and gene expression of sugarcane sucrose synthase gene ScSuSy1and ScSuSy4in those genotypes also showed a remarkable variation during the same growth period. The expression profiles of these genes in high-sugar, medium-and low-sugar genotypes were complex with no clear association between their activity at the early stage of plant growth and final sugar yield of those genotypes. The biological role of ScSuSy1and ScSuSy4gene may change with sugarcane plant development, and may be involved in both the synthesis and decomposition of sucrose.© 2021 Friends Science Publishers