Effects of abiotic stress, light, phytochromes and phytohormones on the expression of OsAQP, a rice aquaporin gene

Water uptake across cell membranes is a principal requirement for plant growth at both the cellular and whole-plant levels. Water movement through plant membranes is regulated by aquaporins. We examined the expression of the OsAQP gene, encodes a tonoplast intrinsic protein (TIP), which was isolated from a rice panicle cDNA library. Semi-quantitative RT-PCR revealed that the gene was ubiquitously expressed in rice roots and leaves. Expression of the gene was up-regulated by drought, salinity and cold in leaves, down-regulated by these abiotic factors in roots, and the gene was also induced by the phytohormones gibberellic acid and abscisic acid in both leaves and roots. Expression of the gene was inhibited by salicylic acid, especially in roots. White light decreased levels of OsAQP transcript, whereas blue light increased expression of the gene. Given that the OsAQP gene is strongly expressed in response to drought, salinity, cold, abscisic acid and gibberellic acid, we propose that OsAQP is a stress-induced gene and that it plays an essential role in the defense of rice against several stresses.