Why and how do plant cells sense sugars?

The ability to sense sugars is crucial for the modulation of gene expression in plants. Despite the importance of this phenomenon, our knowledge of sugar sensing in plants is scant. Several valuable hypotheses have been put forward based on the extensive knowledge of sugar sensing in yeast. In recent years, tests of these hypotheses have shown that hexokinase and sucrose-non-fermenting- (SNF-) related proteins appear to be involved in sugar sensing and transduction, not only in yeast but also in higher plants. However, even if plants share with yeast some elements involved in sugar sensing, several aspects of Sugar perception are likely to be peculiar to higher plants. Plants should be able to sense not only glucose but also other hexoses, Such as fructose and disaccharides (sucrose, maltose and others). In this Botanical Briefing we outline recent discoveries in this field, with emphasis on arabidopsis and cereals. The use of transgenic plants and mutants to identify sugar sensor(s) and elements in the signalling pathways and their cross-talk with the hormonal signalling is discussed. (C) 2001 Annals of Botany Company.