Other Plant AGC Kinases Involved in Auxin Related Processes

In Arabidopsis, PID belongs to the plant specific AGC- (after the cAMP-dependent protein kinase A, cGMP-dependent protein kinase G and phospho-lipids-dependent protein kinase C) VIII subfamily of kinases (Hanks and Hunter 1995). Members of this subfamily show sequence signatures and functional data suggesting that they represent the plant orthologs of the PKA and PKC in animals (Trewavas et al. 2002; Bogre et al. 2003). They do contain peculiar characteristics which distinguish them from their animal counterparts. For example, the classical DFG motif present in subdomain VII of the catalytic kinase domain is replaced by DFD. Furthermore, kinases of the AGCVIII group show an unusual insertion of about 50-80 aa in the activation loop of the catalytic domain. Previous sequence comparisons that were based on

AtAGCI

7_AI1g7gZ50 S_At1g1S440 3 AQg-MBjQ 5_AI3g12690 \ I ~4 At6g<10030

3_Al1gSl170

4_At3g20830

AtAGC2

2_AMg 13000

Fig. 3 Phylogram of the AGCVIII family of protein kinases in Arabidopsis, based on an alignment of amino acid sequence comprising the catalytic domain of these proteins

7_AI1g7gZ50 S_At1g1S440 3 AQg-MBjQ 5_AI3g12690 \ I ~4 At6g<10030

3_Al1gSl170

4_At3g20830

AtAGC3

AtAGC2

2_AMg 13000

Fig. 3 Phylogram of the AGCVIII family of protein kinases in Arabidopsis, based on an alignment of amino acid sequence comprising the catalytic domain of these proteins alignment of complete protein sequences indicated that the Arabidopsis AGC kinases fall into two groups (Bogre et al. 2003). On the basis of an aliment of their catalytic domain, we conclude however that the Arabidopsis AGCVIII kinases fall into the four sub-groups AtAGC1 to 4 (Fig. 3, Galvan and Offringa 2007). It is interesting to note that in this new comparison the phototropins PHOT1 and PHOT2 (AtAGC4) are most closely related to PID and the PID-related kinases (AtAGC3), and that, like PID, the PID-related kinases WAG1 and WAG2 (AtAGC3) and the phototropins are all involved in auxin-mediated plant development. Below we will shortly discuss the roles of these kinases in root waving and blue light-induced responses.

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