Abstract
In the shade avoidance responses, phytochrome is converted to the inactive Pr form, which causes alteration in the expression of various genes. Involvement of plant hormones in this process has been proposed on the basis of whole plant experiments. However, such a system is not ideal to reveal fundamental interactions between phytochrome and hormones occurring in the cell. In the present study, we employed mesophyll protoplast to circumvent the problem. Mesophyll protoplasts were prepared from Arabidopsis rosette leaves and subjected to the end-of-day far-red light treatment. The qRT-PCR analysis confirmed that expression of the AtHB2 gene, a representative marker gene for the response, was induced by the treatment. We then examined effects of exogenously added hormones. Interestingly, auxin increased the AtHB2 expression only when FR was given. Hence, auxin enhanced the shade avoidance response in protoplasts. We are currently examining the possibility that PIF5 is involved in this phenomenon.
