Two novel genes encoding SNF1-related protein kinases from Arabidopsis thaliana: differential accumulation of AtSR1 and AtSR2 transcripts in response to cytokinins and sugars, and phosphorylation of sucrose synthase by AtSR2

Abstract

We searched for genes encoding members of the group-3 SNF1-related protein kinase (SnRK3) family in the Arabidopsis thaliana database, and seven independent sequences were identified. Transcripts of two of them were found to accumulate differentially upon treatment with light, cytokinins and sugars. Full-length cDNAs were isolated and designated as AtSR1 and AtSR2; they encode polypeptides of 442 and 429 amino acids with relative molecular masses of 50.3 kDa and 48.2 kDa, respectively. In etiolated seedlings, no transcripts of either gene were observed. However, upon exposure to light or cytokinins, transcripts of AtSR1 but not AtSR2 began to accumulate. The induction with light was greatly reduced in the presence of a cytokinin antagonist, suggesting that cytokinins are involved in light-signaling pathways. In contrast, transcription of AtSR2, but not of AtSR1, was greatly increased by sucrose, as well as glucose and fructose. AtSR2 expressed in E. coli efficiently phosphorylated sucrose synthase in the presence of manganese ions. These results suggest that, although SnRK3 proteins may generally be involved in sugar metabolism, expression of AtSR1 and AtSR2 is differentially and distinctly regulated by various external signals, and AtSR2 may function in the regulation of sucrose synthase by specific phosphorylation.

Calcineurin B-Like Protein-Interacting Protein Kinase CIPK21 Regulates Osmotic and Salt Stress Responses in Arabidopsis

“…CBLs and CIPKs form complexes that decode the Ca 2+ changes in plant responses to stress signals (Liu et al, 2000;Chikano et al, 2001;Gong et al, 2002;Kim et al, 2003; Pandey, 2008; Luan, 2009;Weinl and Kudla, 2009;Kudla et al, 2010). Although forward and reverse genetic studies have advanced our understanding of the role of these components in Arabidopsis (Pandey et al, 2004D'Angelo et al, 2006;Cheong et al, 2007;Qin et al, 2008;Tripathi et al, 2009;Tang et al, 2012Tang et al, , 2015Drerup et al, 2013), many of the CIPKs are still not functionally characterized.…”

Geminivirus Infection Up-Regulates the Expression of Two Arabidopsis Protein Kinases Related to Yeast SNF1- and Mammalian AMPK-Activating Kinases

“…As a result, plant SnRKs are more diverse and thought to play roles in a variety of cellular processes in addition to nutrient and energy metabolism (Hrabak et al, 2003;Halford et al, 2004). Because of the size and diversity of the Arabidopsis SnRK family, it is likely that their activities are regulated through multiple mechanisms (Chikano et al, 2001). In animals, AMPK can be activated by multiple upstream protein kinases, including the CaMKKs (Hawley et al, 2005;Hurley et al, 2005;Woods et al, 2005) and the AMP-stimulated LKB1 protein kinase .…”

Signaling Pathways Mediating the Induction of Apple Fruitlet Abscission

“…However, also in this case, the majority of these genes are most likely involved downstream of abscission signal generation, except for an Sucrose Non-Fermenting1 (SNF1)-related kinase gene closely similar to Arabidopsis SnRK3. The latter was shown to be induced by exogenous cytokinin (Chikano et al, 2001) and involved in Suc-dependent transcription stimulation of Suc synthase genes (Purcell et al, 1998) and in Suc synthase phosphorylation. Interestingly, a gene coding for a Suc synthase closely similar to Arabidopsis SUS3, induced by Suc and regulated by SnRK3 itself (Chikano et al, 2001), was coregulated in the same samples.…”