Sugars and Circadian Regulation Make Major Contributions to the Global Regulation of Diurnal Gene Expression in Arabidopsis  

Abstract

The diurnal cycle strongly influences many plant metabolic and physiological processes. Arabidopsis thaliana rosettes were harvested six times during 12-h-light/12-h-dark treatments to investigate changes in gene expression using ATH1 arrays. Diagnostic gene sets were identified from published or in-house expression profiles of the response to light, sugar, nitrogen, and water deficit in seedlings and 4 h of darkness or illumination at ambient or compensation point [CO 2 ]. Many sugar-responsive genes showed large diurnal expression changes, whose timing matched that of the diurnal changes of sugars. A set of circadian-regulated genes also showed large diurnal changes in expression. Comparison of published results from a free-running cycle with the diurnal changes in Columbia-0 (Col-0) and the starchless phosphoglucomutase (pgm) mutant indicated that sugars modify the expression of up to half of the clock-regulated genes. Principle component analysis identified genes that make large contributions to diurnal changes and confirmed that sugar and circadian regulation are the major inputs in Col-0 but that sugars dominate the response in pgm. Most of the changes in pgm are triggered by low sugar levels during the night rather than high levels in the light, highlighting the importance of responses to low sugar in diurnal gene regulation. We identified a set of candidate regulatory genes that show robust responses to alterations in sugar levels and change markedly during the diurnal cycle.

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

“…This implies hemicellulose degradation at low Suc levels and supports the idea of hemicellulose and cellulose mobilization to supply energy under Suc-limiting conditions (Contento et al, 2004;Hoch, 2007;Lee et al, 2007). Anticorrelation of profiles for several transcription factors and kinase genes with Suc levels supports the idea that the absence of Suc as the main energyproviding carbon molecule, rather than its presence, has an impact on cellular signaling (Blasing et al, 2005).…”

“…Hence, a significant fraction of those genes might act downstream of, or participate in, a sugar-dependent signaling cascade. In Arabidopsis seedlings, more than 4,000 diurnally fluctuating genes are affected by changing Suc levels and many of the rapidly Suc-induced or -repressed genes correlate either positively or negatively to diurnal Suc levels (Blasing et al, 2005;Osuna et al, 2007).…”

Abiotic stress and the plant circadian clock

“…Similarly cellular sugar levels showed a major contribution in the establishment of diurnal gene expression patterns. 77 Interestingly these authors described that sugar-controlled gene expression was sensitive and responsive to low sugar levels, but not to high sugar. Through the study of the phosphoglucomutase (pgm) mutant, which impaired starch synthesis, they observed that when endogenous sugars levels diminished, sugar responsive genes were rapidly induced.…”

“…Therefore in the wild type, transcriptional reprogramming to declining levels of sugars occurs at the end of the night. 77 It seems that the circadian clock and diurnal changes in carbon availability through photosynthesis are tightly linked and are responsible for many of the cyclic patterns of gene expression under natural day lengths.…”

Catabolismo de sacarose durante a mobilização do galactomanano e sua importância na estratégia de sobrevivência de plântulas de Sesbania virgata (Cav.) Pers.

“…Essas enzimas são importantes em diferentes aspectos do metabolismo de sacarose além das relações de fonte e dreno como regulação osmótica e crescimento celular (Sturm & Tang 1999). Além disso, ao considerarmos que os carboidratos atuam não apenas como substrato para o metabolismo, mas também como moléculas sinalizadoras afetando a expressão de diversos genes (Rolland et al 2002, Blässing et al 2005, a importância da atividade de enzimas do catabolismo de sacarose pode ser estendida a diversos outros processos por possibilitar a alteração das concentrações locais de carboidratos.…”