Plant biology

Tak1 and the Light Harvesting Brigade

Science's STKE  28 Aug 2001:
Vol. 2001, Issue 97, pp. tw1
DOI: 10.1126/stke.2001.97.tw1

Plants are nothing if not adaptable. Depending on the amount and intensity of light, plants can switch between two different light-energy harvesting systems tailored to the energy needs of the plant. Photosystem I (PSI) and PSII utilize a light-harvesting complex protein (LHCP). Under conditions of strong light, LHCP becomes phosphorylated by an unknown kinase and shuttles from PSII to PSI until energy utilization is balanced, at which time LHCP can migrate back to PSII. However, the regulation of LHCP transition between PSII and PSI is unclear. Snyders and Kohorn found that thylakoid-associated kinase 1 (TAK1) is essential for LHCP shuttling. TAK1 formed complexes with LHCP and cytochrome b6f, an important protein in the transfer of light into usable energy. Transgenic plants that expressed TAK1 antisense RNA, and therefore less than the normal amount of TAK1 protein, were stunted in growth--especially under intense-light conditions--and their leaves appeared bleached. These same plants contained lower amounts of phosphorylated LHCP, and decreased migration of LHCP to PSI, which might have been responsible for the plant phenotype. Thus, the data suggest that the activity of TAK1 is essential for the proper regulation of light harvesting in plant thylakoids.

S. Snyders, B. D. Kohorn, Disruption of thylakoid-associated kinase 1 leads to alteration of light harvesting in Arabidopsis. J. Biol. Chem. 276, 32169-32176 (2001). [Abstract] [Full Text]