Control of gene expression in photosynthetic organisms: functional study of SR splicing factors and their role in the alternative splicing process
The regulation of gene expression is a fundamental process in all living beings. In higher eukaryotes, transcription of DNA leads to the synthesis of primary transcripts, the precursor messenger RNAs (pre-mRNAs), consisting of a sequence of exons interrupted by non-coding sequences, introns. Before being transported into the cytoplasm, pre-mRNAs undergo a series of changes that excision-splicing is an essential step in its maturation. This process involves the accurate recognition of introns at splice sites in their excision and ligation of exons. Splicing takes place in a macromolecular structure called the spliceosome (or particle splicing) and requires many different proteins called generically essential splicing factors including SR protein family. They usually have one or two RNA recognition motifs called the RRM (RNA Recognition Motif) N-terminal and rich in serine and arginine (SR or RS) C-terminal domain. In metazoans, they are well characterized and many studies highlight their crucial role in the constitutive splicing involved in the assembly of the spliceosome and their importance in alternative splicing. Alternative splicing can produce different messenger RNAs from a single pre-mRNA, and thus may lead to the synthesis of several protein isoforms. It may therefore have contributed to the morphological and functional complexity in eukaryotic evolution. SR proteins are involved in alternative splicing in participating in the selection of splice sites. * In * Arabidopsis thaliana and Oryza sativa *, * respectively 19 and SR 20 distinct proteins have been identified and are more distinct subclasses. Some of them are homologous to human factors SR. Splicing is an essential mechanism in the subsequent metabolism of mRNAs influencing their stability, cellular localization and efficiency of translation. SR proteins are involved in all of these molecular mechanisms. It was also shown that some human SR proteins are involved in the transport of messenger RNA.
In the lab, we study the SR proteins in Arabidopsis thaliana and Chlamydomonas reinhardtii * different * by cellular, molecular and genetic approaches. We analyze their dynamic localization translational fusion with GFP (Green Fluorescent Protein) after transient transformation of leaf cells and also by stable Arabidopsis transformation and By2 cells (through the study of the cell cycle). Various imaging approaches using confocal microscopy (eg FLIP, FRAP, FRET, the BiFC, ...) are used to study their cellular dynamics, including nuclear-cytoplasmic transport. Vascular plants are advantageous because they allow to study their localization in different cell of the same body type. The functional role of SR proteins in plant development and cell differentiation is initiated by genetic analysis of mutant loss-of-function (insertional mutation or RNA interference).
Metal Homeostasis group - Marc Hanikenne, Research Associate F.R.S.-FNRS
Metal homeostasis mechanisms are studied in photosynthetic organisms (algae and plants). In collaboration with several groups of the department (Profs. M. Galleni, Cl. Remacle, D. Baurain) and teams abroad, molecular physiology, genetics, biochemistry and comparative genomics approaches allow examining:
- the metal deficiency response in C. reinhardtii and plants;
- the mechanisms of zinc and cadmium tolerance and accumulation in the metal hyperaccumulator Arabidopsis halleri.
We are particularly interested in adaptive mechanisms of photosynthetic organisms to their environment, as well as the evolution of these mechanisms.
A better understanding of metal homeostasis in plants will allow the development of innovative approaches for biofortification and phytoremediation.