For optimal growth, plants have evolved strategies to integrate environmental signals to coordinate complex developmental and defensive processes to cope with the changing surroundings. Under challenges, plants prioritize their defense over growth. This trade-off involves complex interactions between multiple hormonal pathways and developmental networks.
We discovered that JACKDAW (JKD), the core component of the SHORTROOT (SHR)-SCARECROW (SCR)- JKD plant developmental regulatory network is linking defense responses to the developmental programming. Unlike the well-studied function of JKD in root development, its function in leaves is yet to be understood.
We found that JKD is expressed on the abaxial side of the leaf ground tissue. It has conserved functions in promoting SHR nuclear retention and restricting cyclinD6 expression in the leaf. Additionally, JKD has a function in leaf internal architecture establishment, including suppression of the bundle sheath cell division and shaping of the leaf ground tissue. We also found that SHR is a universal asymmetric cell division (ACD) activator, as ectopic SHR expression in the leaf ground tissue promotes stomata development via promoting the ACD to produce more stomata precursor cells.
We showed that the knockout mutant of JKD has larger rosettes and better photosynthesis capacity, while the basal defense level and resistance to Botrytis cinerea, a necrotrophic pathogen, are enhanced. Our transcriptome and transcription studies revealed that JKD suppresses the expression of the plant defense hormone Jasmonic acid (JA) response genes and is itself downregulated by JA. This suggests that JKD is involved in the JA signaling, which mediates defense responses for wounding and herbivore attacks. Together, our study indicates that the loss of JKD uncoupled the plant growth-defense trade-off. JKD is a new link between plant development and defense.
To verify whether this function of JKD is conserved in crops, JKD orthologues in tomatoes are identified, CRISPR-Cas9 and TILLING mutants are created and analyzed. The results showed that the functions of JKD in root development and resistance to botrytis are conserved. The broad presence of JKD orthologs makes them a great target for molecular breeding to generate crops that do not have to sacrifice their normal growth to defense response.
|Date of Award||Oct 19 2022|
|Original language||English (US)|
- Biological, Environmental Sciences and Engineering
|Supervisor||Ikram Blilou (Supervisor)|
- leaf development
- JA signaling