Transcription factors for sugar-inducible genes

Abstract

Expression of a variety of sink-related genes for the synthesis of storage compounds are up-regulated in response to increased levels of sugars, while expression of many genes involved in photosynthesis and the breakdown of storage compounds is repressed by sugars. Despite of extensive studies on sugar signaling in plants, only few transcription factors involved in the expression of sugar-inducible genes have been identified so far. A transgenic Arabidopsis thaliana line carrying luciferase gene under the control of a short sugar-inducible promoter derived from a sweet potato sporamin gene was used to screen for loss-of-function type as well as gain-of-function type mutants. These genetic screens resulted in the identification of novel transcription factors that are involved in the expression of at least a subset of sugar-inducible genes in Arabidopsis.

ACRE, a class of AP2/ERF transcription factors, activates the expression of sweet potato ß-amylase and sporamin genes through the sugar-responsible element CMSRE-1

“…Table S1 ). The positive clones included three plant-specific B3 domain proteins such as FUS3 and LEC2 and five homeobox-containing ATHB proteins, both of which have been shown to act on the sugar-responsible minimal promoters through binding to the different cis -element from the CMSRE-1 (Morikami et al 2005b ). Among the rest, we identified two clones, corresponding to At5g21960 and At1g19210, which we designated as A ctivator protein binding to C MS RE -1 1 and 2 (ACRE1 and ACRE2), respectively, after we confirmed that they bound to CMSRE-1 (described below).…”

“…The CMSRE-1 sequence has been shown to be essential for sugar-inducible expression from Spo min and BAD promoters in tobacco and Arabidopsis (Maeo et al 2001 ; Morikami et al 2005a , b ). In sweet potato, it was reported that the Spo min promoter-GUS gene was upregulated by exogenously supplied sucrose in leaves and stems and expressed highly and constitutively in storage roots (Honma and Yamakawa 2019 ).…”

“…This is thought to have been because ACRE1 and ACRE2 weakly bound to the mutated CMSRE-1 or to the sequence other than the CMSRE-1 within the promoter region, and the existence of interactions with other endogenous TFs such as B3 and ATHB family isolated by the same screening of ACRE1 and ACRE2 (Suppl. Table S1 , Morikami et al 2005b ).…”

“…Moreover, we found that a cis element sequence, TGGACGG, designated carbohydrate metabolic signal-responsible element-1 (CMSRE-1), was conserved in both minimal promoters (Maeo et al 2001 ; Morikami et al 2005a ). We attempted to identify TFs that act on this region by using several methods such as yeast-one-hybrid assay using these minimal promoters as bait, enhancer tagging using the reporter gene driven by the minimal promoters, and the screening of mutants exhibiting abnormal expression of sugar-responsible genes are abnormal (Morikami et al 2005b ). However, no TFs acting on CMSRE-1 sequence have been isolated.…”