Tissue-specific Expression of a Dehydrin Gene in One-year-old `Rio Oso Gem' Peach Trees

Abstract

Dehydrins are desiccation-induced proteins. Many plants have several dehydrin genes, some of which are primarily cold induced while others are primarily abscisic acid (ABA) or desiccation induced. Only one dehydrin gene (ppdhn1) has been reported in peach. The dehydrin gene is seasonally regulated and associated with cold acclimation. Because molecular markers for desiccation resistance may aid in the selection of drought- and cold-tolerant genotypes, we sought to determine if ppdhn1 was inducible by desiccation and ABA in all tissues (i.e., a whole-plant response) and to examine the relationship between expression of ppdhn1, desiccation, and dehydrin protein (PCA60). One-year-old `Rio Oso Gem' peach [Pranus persica (L.) Batsch.] trees were maintained at a stem water potential of -2.0 MPa by withholding water for 1 week, followed by daily watering for 1 week for some of the trees. ABA (100 mm) was applied to similar trees that were well watered. Total RNA and protein were extracted from bark, leaves, xylem, and roots, fractionated by electrophoresis, blotted to membranes, and probed with either a peach-specific dehydrin cDNA clone or polyclonal antibodies directed against dehydrin. Accumulation of ppdhn1/PCA60 was induced more by desiccation than ABA applications. Additionally, such accumulation was tissue dependent, being highest in bark tissues and lowest in leaf tissues. The presence of ppdhn1 transcript and corresponding PCA60 protein were not always commensurate with each other. In particular, elevated levels of PCA60 were still present 1 week after desiccation recovery when transcript levels had decreased significantly or were undetectable, indicating that dehydrin is a stable protein. In general, our data indicate that ppdhn1 is similar to other cold-induced dehydrins that are only slightly induced by ABA. In contrast to cold-induced dehydrins, ppdhn1 was strongly induced by desiccation. While synthesis of dehydrin is tightly associated with the onset of stress, disappearance and turnover seem less linked to alleviation of the inducing stress.