Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Abdelali Hannoufa

2nd Supervisor

Susanne Kohalmi

Joint Supervisor

Abstract

Siliques are photosynthetically active seed capsules and their development is strongly influenced by embryo development. MicroRNA156 (miR156)-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) network is involved in regulating plant growth and development, but the downstream genes of this network are still not fully elucidated. Here, I show that the miR156/SPL2 pathway controls the development of floral organs, regulates pollen production, and thus affects male fertility in Arabidopsis thaliana. I present evidence that SPL2 binds to the 5’UTR of the ASYMMETRIC LEAVES 2 (AS2) gene in vivo, indicating that AS2 acts downstream of SPL2. When compared to wild-type plants, AS2 loss-of-function mutants share certain similarities with SPL2 dominant-negative mutants and miR156 overexpression plants, including defective floral organ growth and partially sterile phenotypes. Furthermore, the transcript levels of AS2 were decreased in both miR156 overexpression plants and SPL2 dominant-negative mutant. My results suggest that the miR156/SPL2 pathway and AS2 affect floral organs and silique development as well as plant fertility, and AS2 is directly activated by SPL2.

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