Significance of plasmalemma aquaporins for water‐transport in <i>Arabidopsis thaliana</i>

TLDR

PIP1b, a plasma membrane intrinsic protein, is known to facilitate water transport in plants. The study aimed to determine whether aquaporins are essential for water transport in Arabidopsis thaliana. Researchers generated anti‑sense Arabidopsis lines targeting PIP1b, then measured protoplast swelling in hypotonic solution to assess membrane water permeability. Reduced PIP1b and PIP1a expression lowered cellular water permeability threefold, but increased root mass compensated to maintain water supply, confirming aquaporins’ critical role in plant water transport.

Abstract

Summary The plant plasma membrane intrinsic protein, PIP1b, facilitates water transport. These features were characterized in Xenopus oocytes and it has asked whether aquaporins are relevant for water transport in plants. In order to elucidate this uncertainty Arabidopsis thaliana was transformed with an anti‐sense construct targeted to the PIP1b gene. Molecular analysis revealed that the anti‐sense lines have reduced steady‐state levels of PIP1b and the highly homologous PIP1a mRNA. The cell membrane water permeability was analyzed by swelling of protoplasts, which had been transferred into hypotonic conditions. The results indicate that the reduced expression of the specific aquaporins decreases the cellular osmotic water permeability coefficient approximately three times. The morphology and development of the anti‐sense lines resembles that of control plants, with the exception of the root system, which is five times as abundant as that of control plants. Xylem pressure measurement suggests that the increase of root mass compensates the reduced cellular water permeability in order to ensure a sufficient water supply to the plant. The results obtained by this study, therefore, clearly demonstrate that aquaporins are important for plant water transport.