Abstract
The function of aquaporin (AQP) protein in transporting water is crucial for plants to survive in drought stress. With 47 homologues in tomato (Solanum lycopersicum) were reported, but the individual and integrated functions of aquaporins involved in drought response remains unclear. Here, three plasma membrane intrinsic protein genes, SlPIP2;1, SlPIP2;7 and SlPIP2;5, were identified as candidate aquaporins genes because of highly expressed in tomato roots. Assay on expression in Xenopus oocytes demonstrated that SlPIP2s protein displayed water channel activity and facilitated water transport into the cells. With real-time PCR and in situ hybridization analysis, SlPIP2s were considered to be involved in response to drought treatment. To test its function, transgenic Arabidopsis and tomato lines overexpressing SlPIP2;1, SlPIP2;7 or SlPIP2;5 were generated. Compared with wild type, the over-expression of SlPIP2;1, SlPIP2;7 or SlPIP2;5 transgenic Arabidopsis and tomato plants all showed significantly higher hydraulic conductivity levels and survival rates under both normal and drought conditions. Taken together, this study concludes that aquaporins (SlPIP2;1, SlPIP2;7 and SlPIP2;5) contribute substantially to root water uptake in tomato plants through improving plant water content and maintaining osmotic balance.
Highlights
Hydraulic regulation determines the interplay between water potential gradients and waterflow intensity throughout the whole plant[15]
Transgenic rice plants overexpressing aquaporin RWC3 were more tolerant to drought stress and exhibited higher Lpr compared with non-transformed control plants[35]
Transgenic experiments indicated that SlPIP2s increase plants tolerance to drought stress by improving plant water content and maintaining osmotic balance
Summary
Hydraulic regulation determines the interplay between water potential gradients and waterflow intensity throughout the whole plant[15]. Ding et al found that overexpression of a lily PIP1 gene in tobacco could greatly increase osmotic water permeability of leaf protoplasts and water conductivity of leaf cells[24]. Overexpression of BnPIP1 in transgenic tobacco plants resulted in an increased tolerance to water stress[34]. Transgenic experiments indicated that SlPIP2s increase plants tolerance to drought stress by improving plant water content and maintaining osmotic balance.
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