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Starch and Sucrose Metabolism plays an important role in the Stem Development in Medicago sativa L.

Jierui Wu, Xiaoyu Wang , Lin Bian, Zhenyi Li, Xiaohong Jiang, Fengling Shi , Fang Tang, Zhiqiang Zhang

Abstract

The effect of alfalfa stems on forage quality is greater than that of leaves. The process of sucrose hydrolysis provides energy for stem development, with starch being enzymatically converted into sucrose to maintain energy homeostasis. The interconversion between starch and sucrose plays a pivotal role in the developmental process of alfalfa stems. To gain insight into the physiological and molecular networks controlling stem development in alfalfa, the morphological characteristics and transcriptome profiles in the stems of two alfalfa cultivars (Zhungeer and WL168) were investigated. Moreover, based on the transcriptome data, starch and sugar contents, and enzyme activity related to starch-sugar interconversion were analyzed. The results showed that the stems of Zhungeer were shorter but sturdier compared to WL168, potentially resulting in a significantly higher mechanical strength for Zhungeer. Transcriptome analysis showed that the starch and sucrose metabolism were significant enriched in the DEGs of stems development in both cultivars. In details, genes encoding INV, bglX, HK, TPS and glgC down-regulated gradually with the development of stems in both cultivars, while the gene encoding AMY up-regulated. The WGCNA analysis revealed that the gene encoding glgC played a pivotal role in determining the variations in starch and sucrose contents between the two alfalfa cultivars. Moreover, the soluble carbohydrate, sucrose, and starch content of WL168 were higher in comparison to Zhungeer. The enzyme activities related to sucrose synthesis and hydrolysis including INV, bglX, HK, and TPS showed a downward trend. The change trend of enzyme activity was basically consistent with that of gene expression. The stem of WL168 has higher carbohydrate content than that of Zhungeer which provides a material basis for the rapid growth of WL168, resulting in high plant height of WL168. Hollow stems were formed during the rapid growth of WL168, which may be related to the redistribution of carbohydrates in the pith tissue. These results indicated that starch and sucrose metabolism play important roles in the stem development in alfalfa. Keywords: Medicago sativa L., stems, starch-sugar interconversion, transcriptome, hollow

FP24073  Accepted 18 April 2024

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