Abstract
In higher plants, light and gravity are important parameters in seedling development. PKS1 was identified as a phytochrome interacting factor. In Arabidopsis, PKS1 is a member of a small gene family (PKS1-4) and pks mutants show abnormal phototropism. Moreover, We had shown that PKS1 interacts with PHOT1 and NPH3.
In this study, we show that hypocotyl growth orientation is more complex phenomenon than previously anticipated. Red light inhibits re-orientation of the hypocotyl growth axis when applied from the time of germination. However when applied to hypocotyls undergoing negative gravitropism, red light leads to a deviation from strait growth. Both red light effects require phytochrome signaling and PKS gene family. Moreover, the results of phototropism in pksphot1 and pksphyA combinations suggested that PKS proteins mainly act in the phot1 pathway. We thus propose that PKS proteins may coordinate hypocotyl growth orientation between phytochrome and phot1 dependent responses under low blue light.
