PIP1 Plasma Membrane Aquaporins in Tobacco

TLDR

Aquaporins have well‑characterized molecular functions, yet their role in multicellular plant water transport remains unclear. The study employed the tobacco plasma membrane aquaporin NtAQP1 to investigate its contribution to plant water relations. The authors measured transpiration rate, stem and leaf water potential, and conducted growth experiments under severe soil water depletion to assess the effects of reduced cellular water permeability. NtAQP1 antisense plants exhibited impaired root hydraulic conductivity, lower water stress resistance, and overall reduced cellular and whole‑plant water relations, underscoring the importance of symplastic aquaporin‑mediated transport.

Abstract

The molecular functions of several aquaporins are well characterized (e.g., by analysis of aquaporin-expressing Xenopus oocytes). However, their significance in the physiology of water transport in multicellular organisms remains uncertain. The tobacco plasma membrane aquaporin NtAQP1 was used to elucidate this issue. By comparing antisense plants that were inhibited in NtAQP1 expression with control plants, we found evidence for NtAQP1 function in cellular and whole-plant water relations. The consequences of a decrease in cellular water permeability were determined by measurement of transpiration rate and stem and leaf water potential as well as growth experiments under extreme soil water depletion. Plants impaired in NtAQP1 expression showed reduced root hydraulic conductivity and lower water stress resistance. In conclusion, our results emphasize the importance of symplastic aquaporin-mediated water transport in whole-plant water relations.