Expression of sucrose metabolism and transport genes in cassava petiole abscission zones in response to water stress

Abstract

Cassava (Manihot esculenta Crantz) is an important crop, and its starch formation is regulated by sucrose metabolism and transport. To understand the roles of sucrose metabolism and transport in cassava under water stress, we studied not only sucrose metabolism and transport in cassava abscission zones (AZs) but also expression of respective genes. Sucrose was transported from leaves to roots in the early stage of water stress, and a reverse sucrose flow was detected in the later stages of the stress. The decrease in sucrose content was related to leaf senescence and inhibition of photosynthesis. Microarray analyses showed seven genes encoding sucrose synthase, nine genes encoding sucrose transporters, and eight genes encoding invertase in the cassava AZs under the water stress. Reverse transcription quantitative PCR confirmed two sucrose synthase and two invertase genes significantly upregulated under the stress, whereas one sucrose transporter gene was downregulated. The sucrose synthase and invertase gene expressions were negatively correlated with sucrose content under water stress, whereas sucrose transporter gene expressions were positively correlated with sucrose content.