Emily Eilbert

Date of Award

2014

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Clore, Amy

Keywords

Wall Associated Kinases, Plant Biology, Gravity

Area of Concentration

Biology

Abstract

Wall Associated Kinases (WAKs) are recently discovered Receptor-Like Kinases (RLKs), but their function has proven to be key to plant survival. WAKs are integral plasma membrane proteins with an intracellular serine and threonine kinase domain and the extracellular domain contains Epidermal Growth Factor-like (EGF-like) repeats. WAKs have been found to bind both whole and fragmented strands of pectin, and they are able to distinguish between the two to initiate developmental and defense responses respectively. Furthermore there are multiple types of WAKs which may have different functions. Five WAK genes and isoforms have been found so far in Arabidopsis. WAKs are involved in cell expansion, cell wall biogenesis, and stress responses. Given their involvement in cell expansion and potential role in signaling cascades, I investigated if WAKs were involved in gravitropic cell expansion. Gravity stimulation of a plant stem causes it to bend at approximately a right angle towards the initial vertical position. This response is necessary for survival, and in order for the bending to occur the relative lower half of the stem (closest to the ground after reorientation) must elongate. In Zea mays L., this growth is specific to small disc shaped sections of tissue termed pulvini, which become wedged shaped after gravity stimulation. As an initial step toward testing the potential role of WAKs in maize gravitropism, I imaged WAKs, potential pectin ligands,and microtubules to determine localization patterns in gravity stimulated B73 maize using immunofluorescence. WAK localization indeed changed in the pulvinus tissue during gravity stimulation, suggesting that WAKs are involved in the gravity stimulated response. In addition, there appeared to be partial overlap of signal between the WAKs and microtubules as well as between WAKs and esterified pectin in particular, although confocal microscopy will be necessary for verification.

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