Aquaporin isoforms responsive to salt and water stresses and phytohormones in radish seedlings.
Aquaporins in the plasma and vacuolar membranes play a key role in the intercellular and intracellular water transport in plants. First, we quantitated the absolute amounts for mRNAs of eight aquaporin isoforms in hypocotyls of radish seedlings. Then, we investigated the effects of salt and water stresses (150 mM NaCl, 300 mM mannitol and 20% polyethylene glycol) and phytohormones (gibberellic acid, abscisic acid and brassinolide) on the mRNA and protein levels of aquaporins in the plasma membrane (RsPIP1-1, 1-2, 1-3, 2-1, 2-2 and 2-3) and vacuolar membrane (RsTIP1-1 and 2-1). The mRNA and protein levels of RsTIP1-1, RsTIP2-1, RsPIP1-1, RsPIP1-2 and RsPIP1-3 were comparatively constant. In contrast, mannitol treatment altered the mRNA levels of RsPIP2-1, RsPIP2-2 and RsPIP2-3 in roots. Immunoblot analysis showed that the RsPIP2-1 protein level was increased by NaCl treatment and decreased by treatment with mannitol and polyethylene glycol. Gibberellic acid and abscisic acid suppressed the levels of mRNAs of RsPIP2-1, RsPIP2-2 and RsPIP2-3 and the protein level of RsPIP2-1 in roots. On the other hand, the protein levels of RsPIP1-group members and RsTIPs were scarcely changed by these phytohormones. In the case of hypocotyls and cotyledons, the mRNA and protein levels of eight isoforms were not markedly affected by any treatment. These results indicate that aquaporins in the root, especially the RsPIP2 group, may be a stress responsive type of aquaporin at least in the protein level.
Suga
Shinobu
S
Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan.
Komatsu
Setsuko
S
Maeshima
Masayoshi
M
D000040:Abscisic Acid / Q000494:pharmacology; D020346:Aquaporins / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D060406:Brassinosteroids; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002777:Cholestanols / Q000494:pharmacology; D005875:Gibberellins / Q000494:pharmacology; D018546:Hypocotyl / Q000187:drug effects / Q000378:metabolism; D008353:Mannitol / Q000494:pharmacology; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D020033:Protein Isoforms / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D031224:Raphanus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D013260:Steroids, Heterocyclic / Q000494:pharmacology; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism; D014867:Water / Q000494:pharmacology* / Q000502:physiology
D020346:Aquaporins; D060406:Brassinosteroids; D002777:Cholestanols; D005875:Gibberellins; D010937:Plant Growth Regulators; D020033:Protein Isoforms; D012333:RNA, Messenger; D013260:Steroids, Heterocyclic; D014867:Water; D008353:Mannitol; D011092:Polyethylene Glycols; D012965:Sodium Chloride; D000040:Abscisic Acid; C007842:gibberellic acid; C023623:brassinolide