Wheat cryptochromes: Subcellular localization and involvement in photomorphogenesis and osmotic stress responses

Abstract

Cryptochromes (CRYs) are blue light receptors important for plant growth and development. Comprehensive information on monocot CRYs is currently only available for rice (Oryza sativa). We report here the molecular and functional characterization of two CRY genes, TaCRY1a and TaCRY2, from the monocot wheat (Triticum aestivum). The expression of TaCRY1a was most abundant in seedling leaves and barely detected in roots and germinating embryos under normal growth conditions. The expression of TaCRY2 in germinating embryos was equivalent to that in leaves and much higher than the TaCRY1a counterpart. Transition from dark to light slightly affected the expression of TaCRY1a and TaCRY2 in leaves, and red light produced a stronger induction of TaCRY1a. Treatment of seedlings with high salt, polyethylene glycol, and abscisic acid (ABA) upregulated TaCRY2 in roots and germinating embryos. TaCRY1a displays a light-responsive nucleocytoplasmic shuttling pattern similar to that of Arabidopsis (Arabidopsis thaliana) CRY1, contains nuclear localization domains in both the N and C termini, and includes information for nuclear export in its N-terminal domain. TaCRY2 was localized to the nucleus in the dark. Expression of TaCRY1a-green fluorescent protein or TaCRY2-green fluorescent protein in Arabidopsis conferred a shorter hypocotyl phenotype under blue light. These transgenic Arabidopsis plants showed higher sensitivity to high-salt, osmotic stress, and ABA treatment during germination and postgermination development, and they displayed altered expression of stress/ABA-responsive genes. The primary root growth in transgenic seedlings was less tolerant of ABA. These observations indicate that TaCRY1 and TaCRY2 might be involved in the ABA signaling pathway in addition to their role in primary blue light signal transduction. © 2008 American Society of Plant Biologists.