| Abstrakt: |
Key message: Rhizophora mangle plants tolerate high salinity under field conditions by increasing the transcription of genes involved in photosynthesis, antioxidant system, and salt transport. Rhizophora mangle is a mangrove species adapted to a wide range of salinity and has great ecological importance for mangrove ecosystems. Nevertheless, little is known about the genetic basis underlying the salt-tolerance mechanisms of this species. Here, we investigated the physiological and molecular basis of the salt tolerance in R. mangle under field conditions based on analyses of gas exchange, chlorophyll contents, chlorophyll a fluorescence, and gene expression by qRT-PCR. The gas exchange data showed that the plants growing on both mangrove sites, of low and high salinity, present comparable CO2 assimilation rates and stomatal conductance. Our data suggest that the photosynthetic maintenance under high-salinity conditions was supported by an improved PSII activity, as indicated by chlorophyll a fluorescence parameters and chlorophyll a/b ratio, including the increase of active reaction centers (RCs) and stable oxygen-evolving complexes (OECs). Additionally, the psbA (D1 protein of the RC) and PSBO2 (subunit of the OEC) genes were up-regulated under high salinity, which may be related to increased efficiency to repair injuries in the RC and OEC through the synthesis of new subunits, improving the PSII activity. Likewise, the expression of genes involved in ATP synthesis, RubisCO activation, ROS scavenging, GABA synthesis, and vacuolar Na+ sequestration was up-regulated under high salinity. Thereby, the energy balance and the avoidance of oxidative stress and ion toxicity are also important means by which R. mangle deals with increasing salt levels in natural environments. Taken together, our data shed light on the salt-tolerance mechanisms of R. mangle in its natural ecosystem, including the findings of some possible salt-regulated genes. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink