Sn Rk 202 14 2002

Abstract Sucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs) form a major family of signalling proteins in plants and have been associated with metabolic regulation and stress responses. They comprise three subfamilies: SnRK1, SnRK2, and SnRK3.

SnRK1 plays a major role in the regulation of carbon metabolism and energy status, while SnRKs 2 and 3 have been implicated in stress and abscisic acid (ABA)-mediated signalling pathways. The burgeoning and divergence of this family of protein kinases in plants may have occurred to enable cross-talk between metabolic and stress signalling, and ABA-response-element-binding proteins (AREBPs), a family of transcription factors, have been shown to be substrates for members of all three subfamilies. In this study, levels of SnRK1 protein were shown to decline dramatically in wheat roots in response to ABA treatment, although the amount of phosphorylated (active) SnRK1 remained constant.

First published: 17 January 2002. Cited by: 1285. Figures; Related. Structured interviews were conducted to examine retrospective accounts of lifetime tobacco use in 202 OLT recipients. Sixty percent of OLT recipients reported a.

Multiple SnRK2-type protein kinases were detectable in the root extracts and showed differential responses to ABA treatment. They included a 42 kDa protein that appeared to reduce in response to 3 h of ABA treatment but to recover after longer treatment. There was a clear increase in phosphorylation of this SnRK2 in response to the ABA treatment.

Fractions containing this 42 kDa SnRK2 were shown to phosphorylate synthetic peptides with amino acid sequences based on those of conserved phosphorylation sites in AREBPs. The activity increased 8-fold with the addition of calcium chloride, indicating that it is calcium-dependent. The activity assigned to the 42 kDa SnRK2 also phosphorylated a heterologously expressed wheat AREBP. ,,, Introduction Sucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs) form a major family of signalling proteins in plants and have been associated with metabolic regulation and stress responses (; ).

SnRKs have been grouped into three subfamilies: SnRK1, SnRK2, and SnRK3 (). SnRK1, the homologue of adenosine monophosphate-activated protein kinase (AMPK) from mammals and SNF1 from yeast, has been implicated in the regulation of carbon metabolism and energy status (; ). It controls metabolism at multiple levels; for example, it phosphorylates enzymes such as 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) and sucrose phosphate synthase, leading to their inactivation. Download ebook algoritma gratis. It also phosphorylates nitrate reductase, trehalose-phosphate synthase, and 6-phosphofructo-2-kinase/fructose-2,6- bisphosphatase, but these enzymes also require the binding of a 14-3-3 protein for inactivation (reviewed by ). Another key metabolic enzyme in plants, adenosine diphosphate (ADP)-glucose pyrophosphorylase, is regulated by SnRK1 through modulation of its redox state ().

In addition, SnRK1 causes changes in gene expression in response to nutrient starvation () and, paradoxically, sucrose (; ). The other two SnRK subfamilies, SnRK2 and SnRK3, do not have any counterpart in fungal or animal cells (). They both comprise relatively large gene families, with 10 SnRK2 genes described in Arabidopsis ( Arabidopsis thaliana) and rice ( Oryza sativa) (; ) and 25 SnRK3 genes described in Arabidopsis (). There is now convincing evidence to associate SnRK2 and SnRK3 with responses to abiotic stresses such as drought, salinity, cold, and osmotic stress (). For example, a SnRK3 family member, SOS2 (salt overly sensitive 2), is involved in phosphorylating and activating SOS1, a Na +/H + antiporter, in order to maintain ion homeostasis (; ). A number of SnRK2 family members have been shown to be directly up-regulated and activated by osmotic stress and some but not all of these are also activated by abscisic acid (ABA).