PtHMGR overexpression enhances tolerance of salt and drought

Overexpression of PtHMGR enhanced the stress resistance of poplar.

Aridification and salinization are both threats to usable land. HMGR is a protein used in terpenoids, which have roles in both plant growth and stress responses. Hui Wei and colleagues investigated overexpression of the PtHMGR gene to learn more about improving drought and salinity tolerance in poplar.

Poplar Seedlings. Photo: Professor Qiang Zhuge.

Professor Ali Movahedi, one of the co-authors on the study, said, “This problem of drought and salt important is not only for basic biological research but also of vital importance to breeding and improvements in crop stress resistance. There are a large area of undeveloped and unused land because of drought and salinity existing in China. How to exploit and utilize these lands has become the focus of breeding research.”

Poplar is a particularly good plant for examining this problem, Movahedi said. “Poplar is a species tree that is widely cultivated in temperate and cold temperate regions throughout the Northern Hemisphere. Poplar has been used in studies of perennial plant genomes due to the availability of its genome sequence.”

The current work follows a recent study of DXS and DXR genes in Populus trichocarpa. Movahedi said this was part of a wider study of poplar. “Isoprenoids (or terpenoids) represent a large and diverse group of primary and secondary metabolites present in all living organisms. Several isoprenoid-derived plant hormones regulate plant growth, development, and defense against biotic and abiotic stresses. In the mevalonic acid (MVA) pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) is considered the first rate-limiting enzyme in isoprenoid biosynthesis. In the MEP pathway, 1-deoxy-D-xylulose5-phosphate synthase (DXS) and 1-deoxy-D-xylulose5-phosphate reductoisomerase (DXR) are two rate-limiting enzymes in isoprenoid biosynthesis. In addition, our study was supported by the National Key Program on Transgenic Research (2018ZX08020002). The aim of project is to cultivate poplars resistant to biotic and abiotic stresses.”

While poplar is a commonly studied plant, the team are not sure if the research will be directly applicable to other plants. Movahedi said, “Although plants mainly synthesize ABA through the MEP pathway, and ABA plays an important role in plant abiotic stress, plant physiological and structural differences may have different responses to abiotic stress. In this study, the cross talk may exist in MVA and MEP pathway. Overexpression of PtHMGR affects the expression levels of MEP-related genes, and ultimately increase the accumulation of ABA, thus increasing poplar response to abiotic stress.”

While it might not have direct relevance to other plants, it is a step towards improving poplar productivity. “Our research provides a theoretical basis for poplar breeding,” Movahedi said. “It’s only part of breeding work. Research on transgenic plants is divided into five stages: the experimental stage, the intermediate test stage, the environmental release stage, the productive test stage, the application safety certificate stage, and the commercial production stage. The difference between the intermediate test, environmental release, and productive test stages is the difference in scale (including the number of experimental materials and the planting area), and the difference between the application safety certificate and commercial production stages is the different control condition requirements. Poplar response to abiotic stresses also requires field experiments and biosafety analysis.”

Further reading

Wei, H., Movahedi, A., Xu, C., Sun, W., Li, L., Wang, P., … Zhuge, Q. (2019). Overexpression of PtHMGR enhances the drought and salt tolerance of poplar. Annals of Botany. https://doi.org/10.1093/aob/mcz158