PJB-2018-197
Hydraulic characteristics and aquaporin expression of several apple dwarf rootstocks in response to drought stress
Xiaoyu Han
Abstract
Hydraulic characteristics and aquaporins (AQPs) expression were investigated to explore related hydraulic mechanisms under water deficit conditions using apple dwarfing self-rooted rootstocks i.e. M9, M26, MM106, GM256 and SH6 as materials. In our study, leaf water potential (ψ), photosynthetic indexes, hydraulic characteristics and the expression of PIPs (MpPIP1:1, MpPIP2:1) and TIPs (MpTIP1:1, MpTIP2:1, MpTIP2:2) were measured. The relative expressions of five putative AQPs were determined by Q-RT-PCR. Leaf water potential, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) of aerial parts decreased dramatically when exposed to drought stress. Drought stress reduced slightly root hydraulic conductance (Kr) of the five apple dwarf self-rooted rootstocks, but there was no significant difference between the control group and the drought stress treatment. Moreover, the expression of AQPs in all rootstocks showed a tissue/organ-specific expression pattern. The expression level of MpTIP1:1 in MM106 rootstock leaf is higher than that in the root, while MpPIP1:1, MpPIP2:1, MpTIP2:1, MpTIP2:2 showed greater expression in all rootstocks roots than that in the leaves. Expression of AQPs responses to drought differed greatly in the five rootstocks. There were extremely different expression patterns of PIPs and TIPs genes under drought stress condition, some genes were up-regulated in rootstocks, while others were down-regulated. The lowest value of root hydraulics conductance difference was noted in MM106, which might be caused by a higher expression of MpPIP1:1, MpPIP2:1 and MpTIP2: 1 in MM106 rootstock roots under water stress conditions. Similarly, it exhibited a changed expression patterns of AQPs of different apple dwarf rootstocks induced by drought. AQPs play a positive role in transport of plant-water, maintenance of leaf water potential and promotion of photosynthesis in plants under drought stress condition, which could attribute to improvements in drought tolerance of apple dwarf rootstocks.
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