A pinboard by
A S M Mainul Hasan

PhD candidate, University of Tasmania


The significance of a molecular machinery called mediator complex in ensuring global food security

In 10 seconds? Plants act as primary food producers and play a key role for survival of all other living organisms in the ecosystem. As global population is rising consistently, therefore scientists are constantly innovating molecular genetics based strategies to increase crop yields.

How flowering is important for yield? Flowering time of the plant is directly related to yield as food grains are produced from flowers. Plants decide to flower when the environmental conditions are favourable to do so. Scientists are still lacking detailed knowledge about this mechanism for major crops.

What has been discovered? In the agronomically important crop, pea, two genes namely Cyclin dependent kinase 8 (CDK8) and Cyclin C (CYCC1) which are part of a large molecular machinery called mediator complex (present in major living organisms) found to play important role in regulating flowering time and yield outcome. Besides, they are crucial for survival under environmental stresses such as alteration in temperature and duration of sunlight availability, mechanical injury, UVB exposure and salt stress. Such type of genes are called universal regulators since they regulate function of many other genes and therefore are of high interest for molecular genetics based solution of many agricultural issues.

What is the role of mediator complex? The main role of mediator complex is to control a step of protein manufacturing process called transcription. As genetic information is transferred from genetic element DNA to mRNA, then to protein via molecular processes such as transcription and translation respectively, the ultimate visible outcome is phenotypes like flowering.

Why these findings are so remarkable? The aforementioned findings unveiled significant understanding about the underlying molecular mechanisms that regulate development, reproduction, yield and durability in plants. Such knowledge would assist scientists to deal with serious global issues such as ensuring food security under an altered climatic condition.


The Mediator complex and transcription regulation.

Abstract: The Mediator complex is a multi-subunit assembly that appears to be required for regulating expression of most RNA polymerase II (pol II) transcripts, which include protein-coding and most non-coding RNA genes. Mediator and pol II function within the pre-initiation complex (PIC), which consists of Mediator, pol II, TFIIA, TFIIB, TFIID, TFIIE, TFIIF and TFIIH and is approximately 4.0 MDa in size. Mediator serves as a central scaffold within the PIC and helps regulate pol II activity in ways that remain poorly understood. Mediator is also generally targeted by sequence-specific, DNA-binding transcription factors (TFs) that work to control gene expression programs in response to developmental or environmental cues. At a basic level, Mediator functions by relaying signals from TFs directly to the pol II enzyme, thereby facilitating TF-dependent regulation of gene expression. Thus, Mediator is essential for converting biological inputs (communicated by TFs) to physiological responses (via changes in gene expression). In this review, we summarize an expansive body of research on the Mediator complex, with an emphasis on yeast and mammalian complexes. We focus on the basics that underlie Mediator function, such as its structure and subunit composition, and describe its broad regulatory influence on gene expression, ranging from chromatin architecture to transcription initiation and elongation, to mRNA processing. We also describe factors that influence Mediator structure and activity, including TFs, non-coding RNAs and the CDK8 module.

Pub.: 04 Oct '13, Pinned: 26 Jun '18