A New Progress on Fructose Signaling Pathway in Arabidopsis

A research team led by Prof. Sheng Teng, from Laboratory of Photosynthesis and Environmental Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, discovered a new fructose pathway in Arabidopsis.

In plants, sugars provide the energy and carbon skeletons needed for growth and in addition act as crucial signaling molecules that affect growth, development, and response to the (a)biotic environment. Plant cells harbor sugar-sensing and -signaling systems that regulate the expression of thousands of genes and control the metabolic processes needed for growth. The neutral sugars sucrose, glucose, and fructose are central to metabolism in plants. So far, detailed information is available only on glucose sensing, and it has been shown that the hexokinase 1 (HXK1) enzyme acts as a glucose sensor. Sucrose-speci？c signaling also was demonstrated because the effect of sucrose cannot be mimicked by glucose and/or fructose, but to date no fructose-speci？c signaling pathway has been reported.

In Prof. Teng’s study, sugar repression of seedling development was used to study fructose sensitivity in the Landsberg erecta (Ler)/Cape Verde Islands (Cvi) recombinant inbred line population, and four fructose specific sensitivity quantitative trait loci (QTLs) were identified. Among them, FSQ6 was con？rmed to be a fructose-speci？c QTL by analyzing near-isogenic lines. These results indicate the existence of a fructose-speci？c signaling pathway in Arabidopsis. Further analysis demonstrated that the FSQ6-associated fructose-signaling pathway functions independently of the hexokinase1 (HXK1) glucose sensor. Remarkably, fructose-speci？c FSQ6 downstream signaling interacts with abscisic acid and ethylene signaling pathways, similar to HXK1-dependent glucose signaling. The Cvi allele of FSQ6 acts as a suppressor of fructose signaling. The FSQ6 gene was identified using map-based cloning approach, and FSQ6 was shown to encode the transcription factor gene Arabidopsis NAC domain containing protein 89 (ANAC089). The Cvi allele of FSQ6/ANAC089 is a gain-of-function allele caused by a premature stop in the third exon of the gene. The truncated Cvi FSQ6/ANAC089 protein lacks a membrane association domain that is present in ANAC089 proteins from other Arabidopsis accessions. As a result, Cvi FSQ6/ANAC089 is constitutively active as a transcription factor in the nucleus.

This work was just released in PNAS (Proceedings of the National Academy of Sciences, USA) Online Publication on February 7th, 2011.

This research was supported by Grants from the National Basic Research Program of China, the Ministry of Agriculture of China Project for Transgenic Research, and from the National Science Foundation of China etc. The team led by Prof. Sjef Smeekens in Utrecht University, The Netherlands, is also involved in this research.

Author Contact:
Sheng Teng, Ph.D.
Shanghai Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, The Chinese Academy of Sciences, Shanghai , 200032, China.
Telephone: +86-21-54924159; E-mail: steng@sippe.ac.cn.