Engineering nitrogen storage capacity to improve drought tolerance in plants

Authors: Gupta, Rajeev; ABBARAJU, HARIKISHAN - Corteva Agriscience; APPENZELLER, LAURA - Corteva Agriscience; FALLIS, LYNNE - Corteva Agriscience; HAZEBROEK, JAN - Corteva Agriscience; BOURETT, TIMOTHY - Corteva Agriscience; HOWARD, RICHARD - Corteva Agriscience; LOUSSAERT, DALE - Corteva Agriscience; WEERS, BEN - Corteva Agriscience; LAFITTE, RENEE - Corteva Agriscience; KAKIMI, SALIM - Corteva Agriscience; SCHUSSLER, JEFFERY - Corteva Agriscience; LOUSSAERT, DALE - Corteva Agriscience; HABBEN, JEFFREY - Corteva Agriscience; DHUGGA, KANWARPAL - Corteva Agriscience

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/23/2022
Publication Date: 1/14/2023
Citation: Gupta, R., Abbaraju, H., Appenzeller, L., Fallis, L., Hazebroek, J., Bourett, T., Howard, R., Loussaert, D., Weers, B., Lafitte, R., Kakimi, S., Schussler, J., Loussaert, D., Habben, J., Dhugga, K. 2023. Engineering nitrogen storage capacity to improve drought tolerance in plants. [Abstract]. Plant and Animal Genome Conference. Session Name Climate Change and ICRCGC1.

Interpretive Summary:

Technical Abstract: Environmental stresses, which are becoming more frequent, severe, and unpredictable with changing climate, substantially suppress crop yields below their potential levels. The gap between the actual and potential yield must be narrowed to meet the demand for food grains from a growing and increasingly urbanized world population. Among various abiotic stresses, enhancing drought tolerance or water use efficiency is one of the major targets for crop improvement programs by exploring traditional and novel approaches. We posited that under normal growth conditions there might be periods in plant growth when the leaves produced excess photosynthate than could be utilized for optimal plant growth. The excess photosynthate could be sequestered into an osmoneutral form of reduced N, for example, vegetative storage proteins (VSPs), which could then be remobilized during recovery from transient stresses. For example, during water stress the plant also experiences N stress as delivery of nitrate to the root surface is attenuated. VSPs are known to serve as nitrogen reserves in many dicot plants but remain undiscovered in grasses, most widely grown group of crops globally. We identified and characterized a VSP in maize and demonstrated that its overexpression improved tolerance against water stress imposed around flowering, the most sensitive growth stage to drought. Nitrogen supplementation selectively induced a mesophyll lipoxygenase (ZmLOX6), which was targeted to chloroplasts by a novel N-terminal transit peptide of 62 amino acids. When ectopically expressed under the control of various tissue specific promoters, it accumulated to a five-fold higher level upon expression in the mesophyll cells than the wildtype plants. Constitutive expression or targeted expression specifically to the bundle sheath cells increased its accumulation by less than two-fold. The overexpressed ZmLOX6 was remobilized from the leaves like other major proteins during grain development. Evaluated in the field over locations and years, transgenic hybrids overexpressing ZmLOX6 in the mesophyll cells significantly outyielded non-transgenic sibs under managed drought stress imposed at flowering. Additional storage of nitrogen as a VSP in maize leaves ameliorated the effect of drought on grain yield. In summary, our study provides evidence for the occurrence of a VSP-like protein in maize as well as its contribution to tolerance against water stress when overexpressed in the mesophyll cells. Our results provide a new avenue to improve drought tolerance in plants.