Mechanisms of Water Transport Mediated by PIP Aquaporins and Their Regulation Via Phosphorylation Events Under Salinity Stress in Barley Roots
Mechanisms of Water Transport Mediated by PIP Aquaporins and Their Regulation Via Phosphorylation Events Under Salinity Stress in Barley Roots
复制标题
DOI：
10.1093/pcp/pcr027
复制
发表时间：
2011-04-01
影响因子：
4.9
通讯作者：
Katsuhara, Maki
中科院分区：
文献类型：
--
作者：
Horie, Tomoaki;Kaneko, Toshiyuki;Katsuhara, Maki
水分动态平衡对植物在水分胁迫下的生长和存活至关重要。质膜内在蛋白（PIP）已被证明是介导植物细胞水分吸收的主要通道。在这里，我们报告的水运输活动和机制的调节大麦（大麦）PIP水通道蛋白。发现HvPIP2而不是HvPIP1通道在非洲爪蟾卵母细胞中单独表达时显示出强大的水转运活性。然而，与单独表达HvPIP2相比，在卵母细胞中HvPIP1与HvPIP2的共表达导致活性显著增加，这表明HvPIP1与HvPIP2一起参与水运输，推测是通过异聚化。严重的盐胁迫（200 mM NaCl）显着降低根导水率（Lp（r））和10个HvPIP mRNA的积累。然而，在相对温和的胁迫（100 mM NaCl）下，仅观察到Lp（r）中度降低，而HvPIP mRNA水平无显著差异。山梨醇介导的渗透胁迫相当于100和200 mM NaCl诱导几乎相同的Lp（r）降低大麦根。此外，完整的大麦根中的水运输活动被认为需要磷酸化，这是敏感的激酶抑制剂，星形孢菌素。HvPIP2在非洲爪蟾卵母细胞中也显示出水流出活性，表明在高渗条件下介导细胞失水的潜在能力。讨论了大麦在盐胁迫下通过HvPIP水通道蛋白的水分运输以及Lp（r）降低的意义。
Water homeostasis is crucial to the growth and survival of plants under water-related stress. Plasma membrane intrinsic proteins (PIPs) have been shown to be primary channels mediating water uptake in plant cells. Here we report the water transport activity and mechanisms for the regulation of barley (Hordeum vulgare) PIP aquaporins. HvPIP2 but not HvPIP1 channels were found to show robust water transport activity when expressed alone in Xenopus laevis oocytes. However, the co-expression of HvPIP1 with HvPIP2 in oocytes resulted in significant increases in activity compared with the expression of HvPIP2 alone, suggesting the participation of HvPIP1 in water transport together with HvPIP2 presumably through heteromerization. Severe salinity stress (200 mM NaCl) significantly reduced root hydraulic conductivity (Lp(r)) and the accumulation of six of 10 HvPIP mRNAs. However, under relatively mild stress (100 mM NaCl), only a moderate reduction in Lp(r) with no significant difference in HvPIP mRNA levels was observed. Sorbitol-mediated osmotic stress equivalent to 100 and 200 mM NaCl induced nearly identical Lp(r) reductions in barley roots. Furthermore, the water transport activity in intact barley roots was suggested to require phosphorylation that is sensitive to a kinase inhibitor, staurosporine. HvPIP2s also showed water efflux activity in Xenopus oocytes, suggesting a potential ability to mediate water loss from cells under hypertonic conditions. Water transport via HvPIP aquaporins and the significance of reductions of Lp(r) in barley plants during salinity stress are discussed.