Multiple Signaling Pathways in Gene Expression during Sugar Starvation. Pharmacological Analysis of din Gene Expression in Suspension-Cultured Cells of Arabidopsis

Abstract

We have identified many dark-inducible (din) genes that are expressed in Arabidopsis leaves kept in the dark. In the present study we addressed the question of how plant cells sense the depletion of sugars, and how sugar starvation triggers din gene expression in suspension-cultured cells of Arabidopsis. Depletion of sucrose in the medium triggered marked accumulation of din transcripts. Suppression of din gene expression by 2-deoxy-Glc, and a non-suppressive effect exerted by 3-O-methylGlc, suggested that sugar-repressible expression of din genes is mediated through the phosphorylation of hexose by hexokinase, as exemplified in the repression of photosynthetic genes by sugars. We have further shown that the signaling triggered by sugar starvation involves protein phosphorylation and dephosphorylation events, and have provided the first evidence that multiple pathways of protein dephosphorylation exist in sugar starvation-induced gene expression. An inhibitor of serine/threonine protein kinase, K-252a, inhibited din gene expression in sugar-depleted cells. Okadaic acid, which may preferentially inhibit type 2A protein phosphatases over type 1, enhanced the transcript levels of all din genes, except din6 and din10, under sugar starvation. Conversely, a more potent inhibitor of type 1 and 2A protein phosphatases, calyculin A, increased transcripts from din2 and din9, but decreased those from other din genes, in sugar-depleted cells. On the other hand, calyculin A, but not okadaic acid, completely inhibited the gene expression of chlorophyll a/b-binding protein under sugar starvation. These results indicate that multiple signaling pathways, mediated by different types of protein phosphatases, regulate gene expression during sugar starvation.

Arabidopsis Phosphomannose Isomerase 1, but Not Phosphomannose Isomerase 2, Is Essential for Ascorbic Acid Biosynthesis

“…The transcript and protein levels of PMI1 as well as total level of AsA strongly increased under light and decreased in the dark. In contrast, the transcript levels of PMI2 were not changed under light but increased in the dark as reported previously (48,49), being very low compared with those of PMI1. Therefore, we could not detect the PMI2 protein in crude extracts from leaves using anti-PMI2.…”

“…PMI2 has been previously isolated as a dark inducible gene (Din9), which had undetectable transcript levels in photosynthesizing leaves under light, but substantially increased levels in plants removed from the light for more than 24 h (48,49). In addition, the PMI2 transcript accumulated in sugar-starved suspension cells (48).…”

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

“…These authors also highlight the fact that sugar-limited conditions down-regulated biosynthetic activities to conserve energy and protect cells against nutrient stress. This is usually accompanied by up-regulation of starch degradation to sustain metabolic activity (Yu, 1999;Fujiki et al, 2000).…”

Comprehensive Dissection of Spatiotemporal Metabolic Shifts in Primary, Secondary, and Lipid Metabolism during Developmental Senescence in Arabidopsis

“…However, their roles in senescence remain controversial (Noodén, 1980;Yoshida, 2003;van Doorn, 2004van Doorn, , 2008Wingler et al, 2006Wingler et al, , 2009, since both sugar starvation and addition can induce SAG expression (Gan and Amasino, 1997;Fujiki et al, 2000Fujiki et al, , 2001van Doorn, 2004). Furthermore, although the decline of photosynthesis that occurs during senescence should lead to a decrease of sugar levels, an increase of sugars during senescence was reported in several plant species, including Arabidopsis (Masclaux et al, 2000;Quirino et al, 2001;Stessman et al, 2002;Diaz et al, 2005;Masclaux-Daubresse et al, 2005, 2007Pourtau et al, 2006;Wingler et al, 2006Wingler et al, , 2012.…”