Defining the mechanism that regulates male gametogenesis and floral meristem determinacy by an E3 ubiquitin ligase in Arabidopsis

Project: Research project

Project Details


The life cycle of plants alternates between the diploid sporophyte generation and the haploid gametophyte generation. Upon switching from the vegetative stage to the reproductive stage, the shoot apical meristem of an Arabidopsis plant turns into an inflorescence meristem which gives rise to floral meristem. The stem cells in each floral meristem undergo a limited number of cell division and then terminate their activity to give rise to a defined number of floral organs. An Arabidopsis flower contains anthers where pollen grains (male gametophytes) develop and carpels which are the female reproductive organs. A carpel contains ovules in which female gametophytes are produced. Ovules later develop into seeds following fertilization. The production of viable gametophytes and seeds are essential for plant sexual reproduction.

Recently, we identified an Arabidopsis E3 ubiquitin ligase (PUB4) as a new component that regulates pollen development and floral meristem determinacy. E3 ligases regulate biological pathways by modulating protein stability and activity by catalyzing attachment of ubiquitin units to their specific substrate proteins. This protein ubiquitination targets the substrate proteins for degradation or changes the protein activity. The pub4 loss-of-function causes developmental defects in the tapetal cells. The tapetum is a somatic cell layer in anthers that surrounds developing pollen and undergoes timely programmed cell death at a later stage during male gametogenesis. Proper functioning of the tapetum is essential for pollen development. The pub4 mutation causes unusual enlargement of the tapetal cells and blocks their normal cell death process, leading to male sterility. The pub4 mutation also causes aberrations in floral organogenesis. In the pub4 mutant, ectopic floral organs are formed interior to carpels, indicating that PUB4 also regulates floral meristem determinacy.

The main focus of this proposal is to understand how PUB4 controls the developmental and physiological processes related to pollen development and floral organogenesis. We will use a combination of biochemical, physiological, molecular, and genetic approaches to elucidate specific pathways regulated by PUB4. We aim to identify the targets of PUB4 and additional elements that function in the pathways where PUB4 is involved. Understanding the definitive function of PUB4 will offer novel insights into the genetic networks and the molecular mechanism that regulate these important biological processes.
Effective start/end date1/01/1231/12/14


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