Exploring halotolerant rhizomicrobes as a pool of potent genes for engineering salt stress tolerance in crops

Abstract

Soil salinization is a constant threat to crop productivity and ecology worldwide. The conventional approach, breeding salt-tolerant plant cultivars, has often failed to efficiently alleviate this devastating environmental stress factor. In contrast, the use of a diverse array of microorganisms harbored by plants has attracted increasing attention because of the remarkable beneficial effects of them on plants. Among these microorganisms, halophilic and halotolerant rhizomicrobes is one of the most important extremophilic microorganisms. They can be found in saline or hypersaline ecosystems and have developed different adaptations to sur- vive in salty environments. Their proteins and encoding genes are magnificently engineered to function in a milieu containing 2-5 M salt and represent a valuable repository and resource for reconstruction and visualizing processes of habitat selection and adaptive evolution. Indeed, the natural occurrence of these microor- ganisms in saline soils opens up a possible important role of them in increasing the salt tolerance in crops. They are capable of eliciting physical, chemical, and molec- ular changes in plants which enhanced their tolerance and promoted their growth, and thus they can refine agricultural practices and production under saline condi- tions. Likewise, their ability to serve as bioinoculants could be a more ready utilizable and sustainable solution to ameliorate the deleterious salt effects on plants. However, the ecology of their interactions with plants is still under investigation and not fully understood. This chapter aims to introduce the halotolerant rhizomicrobes and shed light on their special mechanisms to adapt to salinity conditions. A special section would be dedicated for their potential to be exploited in engineering salt tolerance in crops.