The Role of the FLOWERING LOCUS K (FLK) gene in Regulating Defense and Development

Plants are constantly challenged by pathogens and pests. Although being sessile, plants have evolved sophisticated mechanisms to recognize the invaders and activate defense responses. However, defense is an energetically costly process; defense activation can come at the expense of plant development.

Flowering is one of the most critical developmental landmarks in the lifecycle of plants. Prior studies showed that plant defense and flowering time control are connected. However, the molecular basis underlying this connection has not been well understood.

From a large-scale mutant screen in the model plant Arabidopsis that aimed to uncover novel defense genes, we identified a new mutant of a flowering time regulatory gene called FLOWERING LOCUS K (FLK) and our additional data support a defense role of FLK. This project will investigate the dual role of FLK in defense and flowering control. Knowledge obtained from this study shall shed light on how plants coordinate growth, development, and responses to pathogens.

Without such knowledge, our design of strategies in improving the health and yield of crop plants will be limited. Furthermore, this project will provide a platform for the PI to engage students of diverse backgrounds in research training, including a postdoc, a graduate student, and undergraduates, K-12 teachers and high school students from underrepresented minority groups.

Plant defense is a complex process that should be maintained in an intricate balance with development. Increasing evidence indicates the importance of post-transcriptional regulation of plant defense and development by RNA binding proteins. The K homology (KH) repeat is an ancient RNA binding motif found in proteins from diverse organisms.

The role of KH domain proteins in pathogen resistance has not been well known. From a genetic screen for novel defense genes in Arabidopsis, a new allele of the canonical flowering gene FLOWERING LOCUS K (FLK) was identified and was associated with pathogen defense and late flowering. FLK encodes a triple KH-repeat protein.

Data from the PI’s laboratory suggest for the first time that FLK is a multifunctional gene regulating transcript levels and/or alternative splicing of target genes. However, the detailed mechanisms of action of FLK, in particular in defense control, remain to be elucidated. The overall goal of this research is to uncover the molecular basis underlying how FLK and its pathway genes regulate plant defense and development.

The PI will investigate structure-function of the FLK protein, identify and characterize FLK target genes, and characterize FLK interacting proteins in defense and development. Some FLK target genes could uncouple FLK multifunctionality at the molecular level. FLK and FLK pathway genes, especially those that uncouple multifunctionality of FLK, are potentially powerful molecular tools for developing novel biotechnological strategies to precisely control crop traits.

Genome editing could be utilized to modify these genes to improve crop plants with better disease resistance against their natural pathogens while minimizing negative impacts on plant development. Information regarding FLK function, its interactors, and target genes will also provide insights to the study of KH domain proteins in other organisms.

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.