Chrysanthemum morifolium aquaporin genes CmPIP1 and CmPIP2 are involved in tolerance to salt stress

In plants, aquaporin water channels in membranes play a crucial role in abiotic stress tolerance. Here we describe aquaporin genes CmPIP1 (plasma membrane intrinsic proteinl) and CMPLP2 (plasma membrane intrinsic protein2) from the popular ornamental Chrysanthemum moriforrum 'Huoyan'. On the basis of quantitative realtime PCR results, the expression of CmPIP1 and CmPIP2 seems to have a circadian pattern and was highest in leaves; lowest expression for CmPIPI was in stems and in flowers for CmPIP2. There was a close relationship between CmPIP1 or CmPIP2 expression and Na+/K+ ratio in five chrysanthemtun cultivars. When plants were exposed to 300 mM NaCl for 3 days, reductions in fresh mass were smaller in plants that overexpressed CmPIP than in the wild-type or RNAi-CrnPIP transgenic plants; CrnP1P expression in overexpression-transgenic plants was two times higher than in untreated plants, but was almost unchanged in RNAi-CmP/P transgenic plants and wild-type plants. Malondialdehyde content, a stress indicator, increased the least in CmPIP-overexpressing plants and was higher in the FINAi-CmPIP transgenic plants than in the wild-type under salt stress. Thus CmPIP1 and CmPIP2 can improve salt tolerance of chrysanthemum.