Perennial ryegrass (Lolium perenne L.) is one of the most widely used cool-season turf and forage grasses in the world ranging from cold temperate to Mediterranean, and has been found to show wide genetic variation in salt tolerance. Previous studies showed that genetically engineered plants with over-expressing antioxidant genes, thus having higher levels of the relative ROS scavenging enzymes and display improved salt tolerance. However the mechanism of tolerance to salt induced oxidative stress, which is a potential selection criterion for improving plant salt tolerance, has not yet been thoroughly investigated in Perennial ryegrass.

In order to provide answer to this question, a number of related studies have been conducted by Prof. FU Jinmin and his research group at Wuhan Botanical garden. Scientists found that salt stress caused a decrease in turf quality and chlorophyll content, and induced oxidative stress in perennial ryegrass, while the plants have a well-developed complex antioxidant defense system. Under salinity treatments, although the antioxidant gene expression was positively related to the isoenzymatic and total enzymatic activities in leaves of the two perennial ryegrass genotypes, it was higher in salt-tolerant type than in salt-sensitive one during the first 12 days. This result suggests that the constitutive/induced antioxidant gene related to salt tolerance stimulated enzyme activity effectively and improve salt tolerance of perennial ryegrass. In addition, exogenous glycine betaine could ameliorated the adverse effect of salt stress on perennial ryegrass through the elevated antioxidant enzyme activity and alleviation of cell membrane damage by reducing oxidation of membrane lipid and improving the ion homeostasis under salt stress. These results explained the oxidative stress response of perennial ryegrass and contributed to our knowledge of the adaptation of perennial ryegrass to salinity at gene expression, protein level and enzyme activity systems.

Based on above study, a suppression subtractive cDNA library was constructed by using salt-tolerant perennial ryegrass genotype. Differentially expressed cDNA fragments were cloned and screened. BLAST search revealed that 268 clones exhibited significant homologies to known genes. These genes could be categorized into 11 different functional groups, including metabolism, energy transfer, detoxification, compatible solute, cellular transport, transcription, signal transduction, etc. The salinity-regulated expression of selected genes was confirmed by RT-PCR analysis. These results suggested that these putatively salinity up-regulated genes may play vital roles in the salinity tolerance of perennial ryegrass. They can be used as candidate genes for creating stress-tolerant grasses and for understanding molecular mechanisms of plant adaptation to salinity stress.

Main findings of this research have been published in Journal of Plant Physiology, Ecotoxicology and Environmental Safety, and Journal of the American Society for Horticultural Science, respectively. The papers can be accessed at:

http://www.sciencedirect.com/science/article/pii/S0176161711004202