Scientists Uncover Novel Negative Feedback Loop in Sugar-ABA Cascade in Plants

Sugars not only provide energy and carbon skeletons but also act as signaling molecules. In plants, sugar signaling is a central signaling system reflecting the physiological status and the environmental conditions. Sugar signaling are crosstalk with multiple hormone signaling and biotic/abiotic stress signaling. The extensively studied sugar signaling is HXK1-dependent glucose signaling, which stimulates the ABA signaling, thus forming a sugar-ABA signaling cascade. The detailed mechanism of sugar-ABA cascade hasn’t been elucidated yet.

Researchers led by Dr. TENG Sheng in Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences cloned a novel QTL for sugar sensing, GSQ11/ANAC060, which played an important role in the novel negative feedback regulation in the sugar-ABA cascade in plants. These findings bring a new insight into understanding the mechanism of the plant sugar signaling network.

In this study, Arabidopsis thaliana ectypes C24 was found to be supersensitive to sugar. A novel sugar-sensing QTL, GSQ11, was mapped through selective genotyping in Col/C24 F2 sub-population which was extremely insensitive to glucose and confirmed in near-isogenic lines. GSQ11 was further confirmed to encode the NAC family transcription factor with transmembrane domain (TMD) (ANAC060) by candidate mutant analysis, allelism tests and transgenic complementation. The ANAC060 protein occurs as a long or a short version due to differential ANAC060 mRNA splicing caused by a single-nucleotide polymorphism (SNP). The long ANAC060 protein with TMD (C24 type) is located in the cytosol, whereas the short version lacking the TMD (Col type) is always present in the nucleus, where it regulates gene expression.

Further functional studies showed that Col ANAC060 participate in a novel negative feedback loop in the sugar-ABA signaling pathway. ABI4 activates the ANAC060 expression, but the Col ANAC060 inhibited sugar-induced ABA accumulation and ABI4 expression, and reduced sugar sensitivity eventually.

This work entitled “The ABI4-Induced Arabidopsis ANAC060 Transcription Factor Attenuates ABA Signaling and Renders Seedlings Sugar Insensitive when Present in the Nucleus” was published online in PLoS Genetics on Mar 13.
(http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1004213)

This research was supported by The National Science Foundation of China, The Ministry of Agriculture of China for Transgenic Research, the Ministry of Science and Technology of China and The Knowledge Innovation Program of Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

Col ANAC060 mediates the negative feedback regulation in the sugar-ABA signaling pathway. (Image by Dr. TENG Sheng's group)