John Watson, Ph.D.Associate Professor, Biology Department
We study a set protein kinases and their genes from the garden pea, soybean, Arabidopsis in order to understand their role in seedling development.
To identify protein kinases that might transduce light signals, we identified kinase genes whose expression is regulated by light. These pea genes, called PsPK1 through PsPK5, are differentially expressed during de-etiolation in peas.
We now have considerable insight into the function of 4 of the 5 members of the original PsPK series:
(1) PsPK4 and PsPK5 are members of the phototropin 1 family. The phototropins are blue light photoreceptors for phototropism in plants. We showed that PsPK4 encodes a functional blue light photoreceptor for phototropism by transgenic expression in an Arabidopsis phot1 mutant.
(2) PsPK2 encodes the pea homolog of PINOID, which regulates polar auxin transport.
(3) PsPK3 is a close relative of an auxin-inducible kinase from cucumber called CsPK3. PsPK3 polypeptide levels are regulated by light in a pattern distinct from the changes in mRNA levels.
We also study WAG1 and WAG2, the two Arabidopsis homologs of PsPK3, which like PsPK3 are photoregulated at the mRNA level. The distinctive phenotype in wag1/wag2 knockout mutants is constitutive root waving.
Our data suggest that wag phenotype may result from a defect in auxin transport. We are also genetically dissecting the WAG signaling pathway to understand the role of graviperception, auxin transport, and circumnuation in root waving. Work on the soybean homolog of PsPK3 is just beginning.