GIGANTEA â€“ an emerging story

Priyanka Mishra,Kishore C Panigrahi

doi:10.3389/fpls.2015.00008

Priyanka Mishra, Kishore C Panigrahi

Open Access

https://doi.org/10.3389/fpls.2015.00008

Copy DOI

Abstract

GIGANTEA (GI) is a plant specific nuclear protein and functions in diverse physiological processes such as flowering time regulation, light signaling, hypocotyl elongation, control of circadian rhythm, sucrose signaling, starch accumulation, chlorophyll accumulation, transpiration, herbicide tolerance, cold tolerance, drought tolerance, and miRNA processing. It has been five decades since its discovery but the biochemical function of GI and its different domains are still unclear. Although it is known that both GI transcript and GI protein are clock controlled, the regulation of its abundance and functions at the molecular level are still some of the unexplored areas of intensive research. Since GI has many important pleotropic functions as described above scattered through literature, it is worthwhile and about time to encapsulate the available information in a concise review. Therefore, in this review, we are making an attempt to summarize (i) the various interconnected roles that GI possibly plays in the fine-tuning of plant development, and (ii) the known mutations of GI that have been instrumental in understanding its role in distinct physiological processes.

Highlights

GIGANTEA (GI), the unique plant specific nuclear protein, identified way back (Rédei, 1962) as a late flowering mutant in Arabidopsis thaliana (At), its precise biochemical roles are far from being understood
It is interesting to note the ubiquitous expression of GI that reflect upon its pleiotropic roles in multitude of responses ranging from breaking of seed dormancy, hypocotyl elongation, initiating the circadian rhythm in seeds to the setting of fruits in the adult plant
The role of GI in light signaling, circadian clock control, and flowering time regulation seems to be conserved across the plant kingdom, as inferred from the various studies to understand the role of GI homologs in Arabidopsis

Summary

INTRODUCTION

GIGANTEA (GI), the unique plant specific nuclear protein, identified way back (Rédei, 1962) as a late flowering mutant (gi) in Arabidopsis thaliana (At), its precise biochemical roles are far from being understood (de Montaigu et al, 2010). To understand the molecular composition of GI nuclear bodies, attempts were made to evaluate the co-localization of GI with marker proteins of known sub-nuclear compartments such as heterochromatin bundles, nucleoli, spliceosome, and Cajal bodies. This piece of work demonstrated that GI did not localize to any of the above known nuclear compartments (Kim et al, 2013c) This suggested that GI might not have role in processes such as biogenesis of rRNA and snRNP, pre-mRNA splicing, and protein degradation. Since these co-localization studies were carried out in Arabidopsis mesophyll protoplasts using a transient over-expression method, it does not mimic the exact physiological environment. With so many complexities involved, stable transgenic lines expressing fluorescent tagged marker proteins and GI under their native promoters www.frontiersin.org

Mishra and Panigrahi

Highg and BLf

Findings

CONCLUSION AND PERSPECTIVE