Regulation of Sucrose non-Fermenting Related Kinase 1 genes in Arabidopsis thaliana

Abstract

The Sucrose non-Fermenting Related Kinase 1 (SnRK1) proteins have been linked to regulation of energy and stress signaling in eukaryotes. In plants, there is a small SnRK1 gene family. While the SnRK1.1 gene has been well studied, the role other SnRK1 isoforms play in energy or stress signaling is less well understood. We used promoter:GUS analysis and found SnRK1.1 is broadly expressed, while SnRK1.2 is spatially restricted. SnRK1.2 is expressed most abundantly in hydathodes, at the base of leaf primordia, and in vascular tissues within both shoots and roots. We examined the impact that sugars have on SnRK1 gene expression and found that trehalose induces SnRK1.2 expression. Given that the SnRK1.1 and SnRK1.2 proteins are very similar at the amino acid level, we sought to address whether SnRK1.2 is capable of re-programming growth and development as has been seen previously with SnRK1.1 overexpression. While gain-of-function transgenic plants overexpressing two different isoforms of SnRK1.1 flower late as seen previously in other SnRK1.1 overexpressors, SnRK1.2 overexpressors flower early. In addition, SnRK1.2 overexpressors have increased leaf size and rosette diameter during early development, which is the opposite of SnRK1.1 overexpressors. We also investigated whether SnRK1.2 was localized to similar subcellular compartments as SnRK1.1, and found that both accumulate in the nucleus and cytoplasm in transient expression assays. In addition, we found SnRK1.1 accumulates in small puncta that appear after a mechanical wounding stress. Together, these data suggest key differences in regulation of the SnRK1.1 and SnRK1.2 genes in plants, and highlights differences overexpression of each gene has on the development of Arabidopsis.

TaFROG encodes a Pooideae orphan protein that interacts with SnRK1 and enhances resistance to the mycotoxigenic fungus Fusarium graminearum

“…Although further study is required to validate the subcellular location of the complexes, SnRK1 proteins have been previously reported to localize in both the cytoplasm and the nucleus, in agreement with the dual functions of SnRK1 as a regulator of cytosolic enzyme activity and gene expression (Halford and Hey, 2009; Cho et al, 2012). Moreover, SnRK1 can localize in nuclear bodies when interacting with the Domain of Unknown Function581 proteins (Nietzsche et al, 2014) or in cytosolic small fluorescent structures, reflecting both Golgi bodies (O'Brien et al, 2015) or bodies from unknown origins stimulated from mechanical wounding (Williams et al, 2014). Similarly, upon oxidative, metabolic, or drug-induced stress, the AMPK localize in cytosolic bodies (Mahboubi et al, 2015).…”

Phosphorylation of WRINKLED1 by KIN10 Results in Its Proteasomal Degradation, Providing a Link between Energy Homeostasis and Lipid Biosynthesis

“…KIN10 and KIN11 are central transcriptional integrators of stress and energy signaling that are repressed by sugars (Baena-González et al, 2007). Both isoforms are found in the nucleus and cytoplasm; KIN10 is expressed constitutively, whereas KIN11 is restricted to a small subset of tissues (Williams et al, 2014). While KIN10 and KIN11's complementation of the yeast snf1 mutation demonstrates their functional redundancy, recent results suggest that their functions are not completely overlapping because overexpression of KIN10 retards flowering time, whereas overexpression of KIN11 advances it (Williams et al, 2014).…”

“…Both isoforms are found in the nucleus and cytoplasm; KIN10 is expressed constitutively, whereas KIN11 is restricted to a small subset of tissues (Williams et al, 2014). While KIN10 and KIN11's complementation of the yeast snf1 mutation demonstrates their functional redundancy, recent results suggest that their functions are not completely overlapping because overexpression of KIN10 retards flowering time, whereas overexpression of KIN11 advances it (Williams et al, 2014). Overexpression of KIN10 results in the transcriptional activation and repression of more than 1000 genes, the effects of which are to generally increase catabolism and decrease anabolism (Price et al, 2004).…”

Sugar Potentiation of Fatty Acid and Triacylglycerol Accumulation

“…We recently reported a mechanistic explanation for the sugar potentiation of WRI1 (i.e. that SnRK1, encoded by KIN10 and KIN11 in Arabidopsis [Williams et al, 2014], phosphorylates two previously unidentified SnRK1 target sites within WRI1 that marks it for proteasomal degradation [Zhai et al, 2017]). According to the model, under low-sugar conditions, when SnRK1 is active, WRI1 is degraded and lipid synthesis is repressed.…”