Doctorate thesis of Montpellier University

Wednesday, April 4, 2018
14h, Amphi 208

Cell biology of aquaporins in rice (Oryza sativa L.)

Thi Thu Huyen Chu

BPMP, “Aquaporin” team

Jury :
Mme Nathalie LEBORGNE-CASTEL Rapportrice
Mme Nathalie LEONHARDT Rapportrice
M. Laurent NUSSAUME Examinateur
M. Bruno TOURAINE Examinateur
M. Vincent VADEZ Examinateur
M. Doan Trung LUU Directeur de thèse

Abstract :
As molecular players involved into the water transport through biological membranes, aquaporins (AQPs) have a role and are regulated in stress response. They were deeply investigated in plants and particularly in rice. Using functional genetic approach, we generated 5 transgenic rice lines based on Nipponbare cultivar, by overexpressing a single AQP in fusion with a fluorescent marker; among them, 3 plasma membrane AQPs (OsPIP1;1, OsPIP2;4, OsPIP2;5) fused with GFP and 2 tonoplast AQPs (OsTIP1;1 and OsTIP2;2) fused with mCherry. Their subcellular localizations in resting condition were investigated. In rice, OsPIP isoforms showed typical homogeneous labelling of the plasma membrane, whereas OsTIP isoforms were observed localized in the tonoplast with a typical labelling of intracellular invaginations that skirted the nucleus. The behaviors of plasma membrane AQPs were tested in salt and drought stress-mimicked-conditions. Abiotic stresses triggered a re-localization of plasma membrane AQPs and salt stress enhanced endocytosis process of OsPIP2;5 in rice root cells. Overexpressing such transgenes did not seem to affect the plant morphology and showed no beneficial effects for grain yield in both non-stress and stress conditions. We took more focus on the contribution of AQPs in rice root water transport in link with root morphology. AQPs contributed a relative high percentage of water transport in whole root system (44-58%) and seemed to contribute more in primary roots rather than in lateral roots.