Second paper of our Master student Lena Frank originating from her master thesis work. Thanks to Ines and Melina for supervising! We are pleased to have contributed to the paper of Tetsuya Sakai and Ken Haga on the role of AGCVIII kinases in phototropism.

 

Roles of AGCVIII Kinases in the Hypocotyl Phototropism of Arabidopsis Seedlings.

Plant Cell Physiol. 2018 Feb 26.

Ken Haga, Lena Frank, Taro Kimura, Claus Schwechheimer, Tatsuya Sakai 

Regulation of protein function by phosphorylation and dephosphorylation are major regulatory mechanisms in many cellular events. The phototropin blue-light photoreceptors, plant-specific AGCVIII kinases, are essential for phototropic responses. Members of the D6 PROTEIN KINASE (D6PK) family, representing a subfamily of the AGCVIII kinases, also contribute to phototropic responses, suggesting that possibly further AGCVIII kinases may potentially control phototropism. The present study investigates the functional roles of Arabidopsis (Arabidopsis thaliana) AGCVIII kinases in hypocotyl phototropism. We demonstrate that D6PK family kinases are not only required for second but also for first positive phototropism. In addition, we find that a previously uncharacterized AGCVIII protein, AGC1-12, is involved in first positive phototropism and gravitropism. AGC1-12 phosphorylates serine residues in the cytoplasmic loop of PIN-FORMED 1 (PIN1) and shares phosphosite preferences with D6PK. Our work strongly suggests that D6PK family and AGC1-12 are critical components for both hypocotyl phototropism and gravitropism, and that those kinases control tropic responses mainly through regulation of PIN-mediated auxin transport by protein phosphorylation.

 

 

 

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