Photosynthesis is essential to crop productivity and yield. Plants under pathogen attack plants show reduced photosynthetic capacity but the molecular mechanism responsible for this downturn is unknown. It is also unclear whether the reduction is an actively regulated process or a passive result of pathogen infestation and deterioration of plant vigor. In the process of studying the function of two key signaling proteins in plant immunity, it was discovered that the activation of these proteins during pathogen attack rapidly and actively down-regulates various components and activities of the plant photosynthetic apparatus, leading to the generation of reactive oxygen in chloroplasts under light. These events are important to plant resistance against pathogens but at the same time compromise photosynthetic activity. In this project, the investigators will identify unknown components in this pathway. The combination of genomic, molecular genetic, biochemical, and physiological approaches to be used will provide an excellent training environment for students and post-docs. Students (both graduate and undergraduate) and post-docs from under-represented groups will be actively recruited by participating in institutional programs that reach out to minorities. Photosynthesis is key to crop production, and plant defense is always associated with reduced photosynthetic activities, which, in turn, negatively impacts plant growth and yield. Therefore, it is important that we understand the mechanisms that mediate the interaction of these two key functions before we can breed both enhanced immunity and growth/yield in crops by balancing the two sides.
The mitogen activated protein kinases (MAPKs) MPK3/MPK6 participate in plant pathogen-responsive MAPK signaling cascade that plays important roles in both pathogen associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). Long-lasting activation of MPK3/MPK6 during ETI results in active down-regulation of plant photosynthesis via a mechanism which includes mRNA destabilization. Plant defense involves not only up-regulation of gene expression, which has received considerable attention, but also down-regulation. Rapid down-regulation of transcripts of housekeeping genes such as those involved in plant photosynthesis frequently requires mRNA destabilization. Components of the mRNA degradation machinery have been identified, however, the regulatory pathway(s) are largely unknown. In this project the investigators will use an integrative approach to identify and functionally analyze the unknown components in this pathway. Deciphering the mechanism(s) underlying the regulation of mRNA stability by the MPK3/MPK6 cascade during plant immunity is fundamental to our understanding of plant gene expression regulation. Further characterization of MPK3/MPK6 in regulating plant photosynthesis, reactive oxygen species generation in chloroplasts, hypersensitive response mediated cell death, and plant immunity at molecular level will be a major advance in the field. This research will also shed light on the function of MPK3/MPK6 cascade in nucleus-chloroplast communication and retrograde signaling. A deeper understanding of the interplay between photosynthesis and immunity, two processes that have major impacts on crop productivity, should facilitate efforts at crop improvement in support of the production of sufficient food/feed/biofuel to sustain the increasing world population.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
