Far-red light illumination to shoots of Arabidopsis plants causes the repression of an aquaporin gene in roots

Abstract

The transcript of an aquaporin gene, TIP2;2, accumulates in the roots of Arabidopsis plants during dark adaptation, and decreases transiently under far-red light (FR) illumination. To evaluate whether this repression of TIP2;2 in roots is affected by FR illumination to either of organs, we performed northern analyses in the plants whose only shoots or roots are illuminated. When FR illuminated only shoots of wild-type (Ler) plants and a phyB mutant, TIP2;2 mRNA decreased. This repression of TIP2;2 was not observed in a phyA mutant. The results suggest that the phytochrome A signaling pathway is involved in aquaporin gene regulation in roots when shoots are illuminated by FR. Interestingly, TIP2;2 mRNA decreased in Ler, phyA and phyB when the roots were directly illuminated by FR, suggesting that some photoreceptor except for phyA and phyB in roots is also involved in the repression of TIP2;2.