Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada T6E 2E3.
Physiol Plant. 2010 Dec;140(4):321-33. doi: 10.1111/j.1399-3054.2010.01405.x.
We have characterized poplar aquaporins (AQPs) to investigate their possible functions in differential drought responses of Populus balsamifera and Populus simonii×balsamifera leaves. Plants were exposed to mild and severe levels of drought stress and to drought stress recovery treatment, and their responses were compared with well-watered controls. Compared with P. balsamifera, P. simonii×balsamifera used drought avoidance as the main drought resistance strategy, and rapidly reduced stomatal conductance in response to stress. This strategy is correlated with growth rate reductions. Eleven AQPs were transcriptionally profiled in leaves from these experiments and five were functionally characterized for water channel activity. PIP1;3 and PIP2;5 were among the most highly expressed leaf AQPs that were responsive to drought. Expression of PIP1;3 and five other AQPs increased in response to drought in the leaves of P. simonii×balsamifera but not in P. balsamifera, suggesting a possible role of these AQPs in water redistribution in the leaf tissues. PIP2;5 was upregulated in P. balsamifera, but not in P. simonii×balsamifera, suggesting that this AQP supports the transpiration-driven water flow. Functional characterization of five drought-responsive plasma membrane intrinsic proteins (PIPs) demonstrated that three PIP2 AQPs (PIP2;2, PIP2;5, PIP2;7) functioned as water transporters in Xenopus laevis oocytes, while the two PIP1 AQPs (PIP1;2 and PIP1;3) did not, consistent with the notion that they may be functional only as heterotetramers.
我们对杨树水通道蛋白（AQP）进行了特征描述，以研究它们在银白杨和杂种加拿大杨叶片对干旱的不同响应中的可能功能。将植物暴露于轻度和重度干旱胁迫以及干旱胁迫恢复处理下，并将其与充分供水的对照进行比较。与银白杨相比，杂种加拿大杨采用避旱策略作为主要抗旱策略，并在受到胁迫时迅速降低气孔导度。这种策略与生长速率降低有关。在这些实验中，从叶片中对 11 种 AQP 进行了转录谱分析，并对其中 5 种进行了水通道活性的功能表征。PIP1;3 和 PIP2;5 是叶片中表达量最高的 AQP 之一，对干旱有响应。PIP1;3 和其他 5 种 AQP 的表达在杂种加拿大杨叶片中响应干旱而增加，但在银白杨中没有增加，这表明这些 AQP 可能在叶片组织中的水分再分配中发挥作用。PIP2;5 在银白杨中上调，但在杂种加拿大杨中没有上调，这表明这种 AQP 支持蒸腾驱动的水流。对五个响应干旱的质膜内在蛋白（PIP）的功能表征表明，三个 PIP2 AQP（PIP2;2、PIP2;5、PIP2;7）在非洲爪蟾卵母细胞中作为水转运蛋白发挥功能，而两个 PIP1 AQP（PIP1;2 和 PIP1;3）则没有，这与它们可能仅作为异四聚体起作用的观点一致。
