Location: Molecular Plant Pathology LaboratoryTitle: Root-targeted hormonal biotechnology to improve crop stress tolerance Author
Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2011
Publication Date: 2/5/2011
Citation: Ghanem, M.E., Hichri, I., Smigocki, A.C., Albaceta, A., Fauconnier, M., Diatloff, E., Martinez-Andujar, C., Lutts, S., Dodd, I.C., Perez-Alfocea, F. 2011. Root-targeted hormonal biotechnology to improve crop stress tolerance. Plant Cell Reports. 30(5):807-823. Interpretive Summary: Current crop improvement strategies no longer can sustain the growing food needs of the world. To deliver a safe, secure supply of food to a rising global population, while minimizing harmful impacts on cropping ecosystems, will require that the world’s major crops have increased capacity to efficiently utilize shrinking natural resources and to resist diseases and insect pests. One major area that till now has been largely neglected in efforts aimed at crop improvement is the plant root system. The root system has potential for maximizing resource (water, nutrients) capture and coping with environmental stresses (diseases, water deficit, nutrient imbalances, high temperature, soil compaction). Manipulation of plant root systems could conceivably produce improved crops with significantly sustainable, elevated yields. We studied the effect of plant hormones (growth regulators) on root system architecture and plant responses to environmental stresses. Our results demonstrate that manipulation of plant hormones in the root system alters plant root architecture, improving the plant’s ability to tolerate a range of environmental stresses (salt, heavy metals, flooding, diseases, pests). This information will be used by scientists developing crops having an improved root system that is capable of mitigating the effects of environmental stresses.
Technical Abstract: Since plant root systems capture both water and nutrients essential for the formation of crop yield, there has been renewed biotechnological focus on root system improvement. Although water and nutrient uptake can be facilitated by membrane proteins known as aquaporins and nutrient transporters respectively, there is little evidence that overexpression of these proteins only in the roots improves plant growth or stress tolerance. Recent work suggests that the major classes of phytohormones are involved not only in regulating aquaporin and nutrient transporter expression and activity, but also in sculpting root system architecture. Root specific expression of plant and bacterial hormone-related genes, using either root specific or root-inducible promoters, or grafting non-transformed plants onto constitutive hormone producing rootstocks, has allowed evaluation of the role of root hormone production in mediating crop stress tolerance. Putatively root specific expression of bacterial ACC deaminase (an enzyme which degrades the precursor of the plant stress hormone ethylene) increased shoot growth under a range of stresses (salt, heavy metals, flooding). In contrast, root synthesised ABA seemingly had little role in regulating shoot growth and water use. Root specific expression of the IPT gene (for de novo synthesis of the plant hormones cytokinins) attenuated growth inhibition and delayed leaf senescence caused by salinity, and are suggested (based on their ability to deter foliar insect feeding) to enhance root resistance to below-ground pests. Further advances in instrumentation are required to understand the role of phytohormones and other volatile compounds in below-ground interactions between plants and soil, and plants and rhizosphere organisms.