Authors: T Ohrui H Nobira Y Sakata T Taji C Yamamoto K Nishida T Yamakawa Y Sasuga Y Yaguchi H Takenaga Shigeo Tanaka
Publish Date: 2007/08/03
Volume: 227, Issue: 1, Pages: 47-56
Abstract
The atmospheric epiphyte Tillandsia ionantha is capable of surviving drought stress for 6 months or more without any exogenous water supply via an as of yet to be determined mechanism When plants were soaked in water for 3 h leaves absorbed a remarkably large amount of water 30–40 on the basis of fresh weight exhibiting a bimodal absorption pattern Radiolabeled water was taken up by the leaves by capillary action of the epidermal trichomes within 1 min phase 1 and then transported intracellularly to leaf tissues over 3 h phase 2 The removal of epidermal trichome wings from leaves as well as rinsing leaves with water significantly lowered the extracellular accumulation of water on leaf surfaces The intracellular transport of water was inhibited by mercuric chloride implicating the involvement of a water channel aquaporin in secondphase water absorption Four cDNA clones TiPIP1a TiPIP1b TiPIP1c and TiPIP2a homologous to PIP family aquaporins were isolated from the leaves and RTPCR showed that soaking plants in water stimulated the expression of TiPIP2a mRNA suggesting the reinforcement in ability to rapidly absorb a large amount of water The expression of TiPIP2a complementary RNA in Xenopus oocytes enhanced permeability and treatment with inhibitors suggested that the water channel activity of TiPIP2a protein was regulated by phosphorylation Thus the high water uptake capability of T ionantha leaves surviving drought is attributable to a bimodal trichome and aquaporinaided water uptake system based on rapid physical collection of water and subsequent sustained chemical absorption
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