Sugar Coordinately and Differentially Regulates Growth- and Stress-Related Gene Expression via a Complex Signal Transduction Network and Multiple Control Mechanisms

Abstract

In plants, sugars are required to sustain growth and regulate gene expression. A large set of genes are either up-or down-regulated by sugars; however, whether there is a common mechanism and signal transduction pathway for differential and coordinated sugar regulation remain unclear. In the present study, the rice (Oryza sativa cv Tainan 5) cell culture was used as a model system to address this question. Sucrose and glucose both played dual functions in gene regulation as exemplified by the up-regulation of growth-related genes and down-regulation of stress-related genes. Sugar coordinately but differentially activated or repressed gene expression, and nuclear run-on transcription and mRNA half-life analyses revealed regulation of both the transcription rate and mRNA stability. Although coordinately regulated by sugars, these growth-and stress-related genes were up-regulated or down-regulated through hexokinase-dependent and/or hexokinaseindependent pathways. We also found that the sugar signal transduction pathway may overlap the glycolytic pathway for gene repression. ␣-Amylase and the stress-related genes identified in this study were coordinately expressed under sugar starvation, suggesting a convergence of the nutritional and environmental stress signal transduction pathways. Together, our studies provide a new insight into the complex signal transduction network and mechanisms of sugar regulation of growth and stress-related genes in plants.

Differential Anoxic Expression of Sugar-Regulated Genes Reveals Diverse Interactions between Sugar and Anaerobic Signaling Systems in Rice

“…Moreover, such adjustments should be closely coordinated to maintain harmonious physiology (Koch et al, 2000). Many stress-related genes were found to be coordinately expressed under sugar starvation, either via hexokinase-dependent or independent pathways in rice (Ho et al, 2001). Such sugar regulated expression of many stress-related genes suggested two signaling cascades of the nutritional and environmental stress would be converged at certain point of the pathway.…”

“…3B). Previously, Ho et al (2001) found that treatment of 2-deoxyglucose up to 0.5 mM was toxic to suspension cultured rice cells. However, no significant deterioration of total RNA isolated from 2-deoxyglucose treated cells was observed in our examination of ethidium bromide staining of rRNA.…”

The SnRK1A Protein Kinase Plays a Key Role in Sugar Signaling during Germination and Seedling Growth of Rice

“…Sugars modulate nearly all fundamental processes throughout the entire life cycle of plants, including embryogenesis, germination, growth, development, reproduction, senescence, and responses to diseases and environmental stimuli (Smeekens, 2000;. In general, sugars upregulate genes involved in biosynthesis, transport, and storage of reserves and cell growth and downregulate those associated with photosynthesis, reserve mobilization, and response to stresses (Graham, 1996;Koch, 1996;Ho et al, 2001). Studies with Arabidopsis thaliana and rice (Oryza sativa) have revealed intimate interaction between sugar and plant hormones, environmental stimuli, and metabolic signaling pathways (Sheen et al, 1999;Gibson, 2000;Smeekens, 2000;Coruzzi and Zhou, 2001;Gazzarrini and McCourt, 2001;Rolland et al, 2002Rolland et al, , 2006Hong et al, 2003;Chen et al, 2006).…”

Novel Gene Encoding a Ca2+-Binding Protein and under Hexokinase-dependent Sugar Regulation

“…30) The signal transduction pathways in which sugars function are complex, with multiple mechanisms of regulation. 31,32) In an attempt to investigate the sugar response in plants, we isolated from rice embryos cDNAs that are either up-or down-regulated by sugars using cDNA microarray technology. We characterized a novel cDNA, OsSUR1, that is up-regulated by sugar and Fig.…”