Document Type

Open Access Thesis

Embargo Period

9-1-2017

Degree Program

Biology

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2016

Month Degree Awarded

September

Advisor Name

Elsbeth

Advisor Last Name

Walker

Abstract

Iron is among the essential micronutrients for all living organisms and is a cofactor for many cellular redox reactions. Although iron is a highly abundant metal element found in the earth’s crust, it is also a limiting factor in plant development when it is present as insoluble ferric oxides. Plants have evolved two strategies to acquire soluble iron referred to as Strategy I and Strategy II. Our lab has focused on the Arabidopsis thaliana double mutant ysl1ysl3. The mutants display a chlorotic phenotype and are unable to correctly respond to iron deficiency.

Grafting is a common method for joining different plant tissues and has been used for studies of long distance signaling. Past studies of iron signaling in Arabidopsis have not been able to provide a mechanism for how plants are able to signal the iron status of the shoot, where iron demand is high, to roots, where iron uptake occurs. The iron signaling experiments included in this thesis follow a seedling-graft approach to understand if grafts are capable of properly sensing iron.

A longstanding question of iron homeostasis in plants is the identity of the iron sensors in plants. It was hypothesized that YSL1 and YSL3 have both a transporter function and a receptor function, and therefore function as transceptors. In our predicted model it was proposed that YSL1 and/or YSL3 are directly involved in iron status signaling either in perception and/or transmission of the signal. As evidenced through seedling grafting experiments here, YSLs play a critical part of long distance signaling that plant shoots use to signal their iron status to the roots. In this thesis, YSL1 and YSL3 are shown to be required in the shoots in order for signaling to occur correctly in the roots. To facilitate the analysis of gene expression in the grafts, a FRO3promoter:GUS construct was used in the Col-O WT background. The FRO3 promoter was selected because it is expressed in both leaves and roots under iron deficiency. Experiments showed that the genotype of the shoot used in the grafts is critical for Fe-deficiency induced gene expression in the roots. Thus, grafting has revealed that root iron deficiency responses require YSL1 and YSL3 in leaves for signal transmission. This directly links them to long-distance signaling, and supports the idea that these proteins could be acting as transceptors.

Included in

Plant Biology Commons

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