ORYZAQUA

Cell biology of rice aquaporins

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 Obiettivo del progetto (Objective)

'Although they are exposed to ever changing and sometimes challenging environmental conditions, higher plants can achieve remarkable metabolic and growth performances. For this, they have to precisely maintain their water status and failure to do so can dramatically impact their growth and ultimately their survival. The control of water flow in the soil-plant-atmosphere continuum and the fine-tuning of water transport within the plant body represent important mechanisms in these respects. Because of their role in soil water uptake, roots are central during these processes. The project for this fellowship is to develop rice as a model for understanding the function and regulation of aquaporins at the cellular level : 1. Aquaporin function and sub-cellular localisation will be investigated in two rice cultivars one upland and lowland, adapted to different watering conditions. Upland rice is grown in rain fed fields prepared and seeded when dry. With respect to this, upland rice can be considered as a classical model cereal, such as wheat or maize. Lowland rice is grown in submersion with water (paddy fields) until ripening. Studying these two types of rice will offer unique opportunity to gain insight about how aquaporin function and sub-cellular localisation can contribute to the adaptation of the plant to two contrasted watering culture systems. 2. As architecture of the rice root is complex, we will consider each of the 4 types of roots in our project. One question will be to better understand which type of roots is more important for water uptake and regulation. 3. The project will allow identifying the subcellular regulation of rice root aquaporins in response to stimuli such as drought and salt.

The present project will target a major crop using state-of-the-art knowledge on physiological, molecular and genetic processes obtained in the plant model Arabidopsis.'

Introduzione (Teaser)

Plant scientists have investigated the adaptive mechanism in plant roots that enables them adapt to non-biological stress such as salinity and drought.

Descrizione progetto (Article)

It is predicted that in the next 20 years almost half of the world will be facing severe water stress. Therefore, plant science technologies should be employed to protect this vital resource by improving water-use efficiency in crops.

Rice is a major food crop around the world, but little is known about its aquaporin function and water regulation at the cellular level. The EU-funded 'Cell biology and rice aquaporins' (ORYZAQUA) project addressed these gaps in knowledge in different rice cultivars and changing conditions.

Aquaporins are proteins in the plasma membrane of plant cells that act as water channels and are critical to water regulation. Hydraulic conductivity, water permeability and osmotic potential regulation are some of the key factors involved in water regulation in plants.

ORYZAQUA researchers studied a range of rice aquaporins, root architecture and hydraulics, and subjected them to salt stress and drought conditions. This was then compared to stress-free conditions. In addition, researchers successfully cloned rice aquaporin sequences and tagged them with fluorescent protein (FP); the transformation of other rice isoforms and cultivars is ongoing.

Researchers successfully cloned the fluorescently-tagged OsRabr sequence (aquaporin) for co-expressing endomembrane markers tagged with the mCherry FP. Work was also conducted to express other aquaporin sequences that include OsGAP1 and OsNST1. Studies were also carried out to assess aquaporins' sub-cellular localisation and function in stressed and stress-free conditions in these rice plants.

Work conducted by ORYZAQUA established for the first time the strong inhibitory effect of salinity on the root water transport of young rice plants. It showed a physiological mechanism that can respond to environmental challenges within an hour. Since this inhibitory effect is so rapid, it indicates that the regulation of aquaporin activity is a significant factor in whole-plant response to salinity.

The project will help explain complex interactions between the molecular pathways for signalling in response to abiotic stress and those controlling cell and organ responses. It will also help to improve agricultural production through better adaptation to climate change and to develop agriculture in marginal lands.