Why and how do plant cells sense sugars?

The ability to sense sugars is crucial for the modulation of gene expressio n in plants. Despite the importance of this phenomenon, our knowledge of su gar sensing in plants is scant. Several valuable hypotheses have been put f orward based on the extensive knowledge of sugar sensing in yeast. In recen t years, tests of these hypotheses have shown that hexokinase and sucrose-n on-fermenting- (SNF-) related proteins appear to be involved in sugar sensi ng and transduction, not only in yeast but also in higher plants. However, even if plants share with yeast some elements involved in sugar sensing, se veral aspects of Sugar perception are likely to be peculiar to higher plant s. Plants should be able to sense not only glucose but also other hexoses, Such as fructose and disaccharides (sucrose, maltose and others). In this B otanical Briefing we outline recent discoveries in this field, with emphasi s on arabidopsis and cereals. The use of transgenic plants and mutants to i dentify sugar sensor(s) and elements in the signalling pathways and their c ross-talk with the hormonal signalling is discussed. (C) 2001 Annals of Bot any Company.