Date of Award

5-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Elena D. Shpak

Committee Members

Barry D. Bruce, Karen W. Hughes, Bruce D. Mckee, Albrecht G. von Arnim

Abstract

Intercellular communication is indispensable for development of complex multicellular organisms. Cell to cell communication in plants is heavily reliant on receptor-like-kinases (RLKs) located on the surface of cells. ERECTA (ER) and its two paralogs ERECTA-like 1 (ERL1) and ERL2 are leucine-rich repeats RLKs that regulate multiple developmental processes. Ligands of the ERf receptors are small secreted peptides known as Epidermal Patterning Factor-Like (EPFL). In Arabidopsis, the EPFL family is made of 11 genes, several of which remain to be characterized. Results presented in this work include:1) The use of structure function analysis found that juxtamembrane domain and kinase activity is essential for ERECTA signaling activity while the carboxy-terminal tail is not. Analysis of the activation loop in the kinase domain revealed the importance of phosphorylation sites that modulate the signaling of ERECTA. Lastly, not all developmental processes regulated by the ERECTA family require kinase activity suggesting that there are different mechanisms for stomata development and regulation of organ growth.2) Ectopic expression of ERECTA in specified regions of the shoot apical meristem (SAM) releveled that central zone expression was sufficient to rescue the meristem size and leaf initiation defects of er erl1 erl2 mutant. Transcriptional reporter lines identified the putative ER family ligands that were expressed near the SAM. A genetics approach reveled EPFL1, EPFL2, EPFL4 and EPFL6 to redundantly regulate meristem size and rate of leaf initiation. Lastly, ectopic expression of EPFL1 in the peripheral zone of the SAM rescued SAM phenotypes of the epfl1 epfl2 epfl4 eplf6 mutant. These results suggest that the ERECTA family signaling pathway mediates communication between the peripheral zone and central zone of the SAM.This work expands our knowledge of ERECTA family signaling and its implementation in the role of SAM regulation.

Orcid ID

http://orcid.org/0000-0001-5009-4488

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