Ethylene Responsive Factor MeERF72 Negatively Regulates Sucrose synthase 1 Gene in Cassava

Abstract

Cassava, an important food and industrial crop globally, is characterized by its powerful starch accumulation in its storage root. However, the underlying molecular mechanism for this feature remains unclear. Sucrose synthase initializes the conversion of sucrose to starch, and, to a certain extent, its enzyme activity can represent sink strength. To understand the modulation of <i>MeSus</i> gene family, the relatively high expressed member in storage root, <i>MeSus1</i>, its promoter was used as bait to screen cassava storage root full-length cDNA library through a yeast one-hybrid system. An ethylene responsive factor cDNA, designated as <i>MeERF72</i> according to its homolog in <i>Arabidopsis</i>, was screened out. The transcript level of <i>MeERF72</i> was induced by ethylene, drought, and salt treatments and repressed by abscisic acid, Auxin, gibberellin, salicylic acid, and low and high temperatures. The MeERF72 protein has a conserved APETALA2 domain in its N-terminus and an activated domain of 30 amino acids in its C-terminus, can bind to <i>MeSus1</i> promoter in vitro and in vivo, and represses the promoter activity of <i>MeSus1</i>. MeERF72 is a transcription factor that can negatively regulate the expression level of <i>MeSus1</i> in cassava.