To do this we are examining the group of genes known as CRFs or Cytokinin Response Factors in both Arabidopsis and tomato. CRF are transcription factors that are named after the AP2/ERF or Ethylene Response Factor family of which they are members.

We are also focused on understanding the role of N-Conjugated Cytokinin forms, where a glucose has been added to the N7 or N9 position of different base cytokinin forms, such as trans-Zeatin. N-conjugated cytokinins are often noted in the literature as being inactive in standard cytokinin-related processes, but we have been able to show they can actively function to delay senescence similar to their base forms. Further investigations of N-conjugate roles are on-going in the lab and are currently funded by NSF grant.

We are taking similar approaches (molecular, genetic, and phenotype analyses at the whole plant, tissue and cellular level) in both Arabidopsis and tomato to understand the role of CRFs in cytokinin based growth and development as well as in abiotic stress responses.

CRFs in Arabidopsis

In Arabidopsis we have made full use of the tools available in this genetic model system to study CRFs. Mutants, transcript and genomic analyses, bioassays, and protein movement studies have generated the baseline of information on CRFs. We are continuing to build on these results to gain a better understanding of how and where CRFs function in plant development and abiotic stress responses.

CRFs in Tomato (SlCRFs)

In tomato we identified and characterized all the SlCRFs in this species, including establishing basic tissue expression patterns and hormonal response of SlCRFs to cytokinin. Recent work is focused on responses to abiotic stress as well as generally determining their functional roles. Connections between Arabidopsis and tomato functional orthologs are being explored using approaches as noted above for Arabidopsis studies.

CRF Phylogeny and Clade alignment figures from Zwack et al., 2012