Heterotrimeric G-proteins are present in all eukaryotic organisms from simple fungi to humans and plants. The proteins regulate critical growth and development processes in these organisms by acting as molecular switches. While extensively studied in humans due to their involvement in a multitude of diseases and neurotransmission, the knowledge of G-protein signaling mechanisms and their significance in plants remains relatively scarce. Pandey and colleagues were first to discover G-protein in green algae, confirming that the proteins existed early on during plant evolution. In their recent work in collaboration with Dr. Ralph Quatrano鈥檚 group at Washington University in St. Louis, they discovered that G proteins are essential for the life cycle completion in moss, a non-vascular plant of basal plant lineage. Moss, which has a predominant gametophytic life style, interspersed with a short sporophytic phase, failed to form sporophytes (the only diploid stage in its life cycle) when specific G-protein subunits were genetically removed. This is significant because prior to this work, the plant G-proteins were thought to be non-essential and modulatory in nature. Results of this research were published in the journal, Plant Physiology titled 鈥淪porophyte formation and life cycle completion in moss requires heterotrimeric G-proteins鈥� Aug 22. pii: pp.01088.2016.
One of the key focus areas of the Pandey lab research is to uncover both conserved and unique signaling mechanisms and components of heterotrimeric G-proteins in plants. To address some of the questions related to the proposed loss of one of the key regulatory proteins of the G-protein complex, the Regulator of G-protein Signaling (RGS) protein in the monocot lineage, they performed a large evolutionary and structure/function analysis in collaboration with Dr. Toby Kellogg鈥檚 lab at the Danforth Center and Dr. Joe Jez鈥檚 lab at Washington University. Their results challenged the current dogma in the field and confirmed that the RGS proteins are wide-spread in the monocot lineage, despite their frequent loss. This research also showed that the functional interface between the G-protein 伪 subunit and the RGS proteins is conserved across all organisms including between plants and humans. This research is recently published in the journal, New Phytologist, titled 鈥淕伪 and Regulator of G-protein Signaling (RGS) protein pairs maintain functional compatibility and conserved interaction interfaces throughout evolution despite frequent loss of RGS proteins in plants.鈥�
In an attempt to identify additional proteins that possess similar biochemical activities as the RGS proteins, the Pandey lab also identified the role of a type of lipid hydrolyzing proteins, the phospholipase D伪1 (PLD 伪1) in regulating G-protein cycle. This research provided clues to additional proteins that are involved in the regulation of G-protein signaling pathways in plants, and added significantly to the diversity that may exist in plants鈥� regulatory mechanisms. This research also demonstrated that the same G-protein subunits and their modulators exhibit distinct physiological and genetic interactions depending on specific signaling and a developmental pathway which helps to fine tune the plants鈥� responses to constantly changing environments. These findings were recently published in The Plant Journal in an article titled 鈥淭he role of PLD伪1 in providing specificity to signal-response coupling by heterotrimeric G-protein components in Arabidopsis鈥� 86(1):50-61. doi: 10.1111/tpj.13151. Additional, more directly applied aspects of research in the Pandey lab are related to the regulation of nodule formation in legumes such as soybeans and yield enhancement by controlling seed size and seed number. They recently discovered the role of G-proteins in regulation of nodule formation in soybean and uncovered a signaling pathway where the receptors of Nod factor perception interact with and phosphorylate G-protein components to control nodule number in plants. This research was published in The Plant Cell titled 鈥淧hosphorylation-Dependent Regulation of G-Protein Cycle during Nodule Formation in Soybean鈥� 27(11):3260-76. doi: 10.1105/tpc.15.00517.
The research related to yield improvement in crops is related to a newly discovered subunit of G proteins, the type III G纬. The Pandey lab was first to discover it in soybeans and it was simultaneously reported in Arabidopsis from two additional groups. The research from Pandey鈥檚 lab and others鈥� has confirmed the role of type III G纬 proteins in improved yield, nitrogen use efficiency and stress responses. This work has led to important hypothesis development about several unanswered questions related to the action mechanism of these proteins, for which Pandey has been recently awarded a grant from the National Science Foundation.
鈥淕 proteins, alpha, beta and gamma and their modulators are important because they play critical roles in plants鈥� development, including fruit and seed size and production, defense against pests and pathogens and response to abiotic stresses such as drought and ozone,鈥� Pandey said. 鈥淯nderstanding their function at the very basic level is an important step in the process of developing products that can be applied to improve crop yield and address environmental issues related to production agriculture.鈥�
Ongoing research in the Pandey lab seeks to improve crops that require less nitrogen-containing fertilizer and limit stress factors to increase yield by understanding the regulatory mechanisms and structure/function relationships of important signaling proteins in plants.
About The Donald Danforth Plant Science CenterFounded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research aims to feed the hungry and improve human health, preserve and renew the environment and position the St. Louis region as a world center for plant science. The Center鈥檚 work is funded through competitive grants and contract revenue from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, U.S. Department of Agriculture, U.S. Agency for International Development, the Bill & Melinda Gates and Howard G. Buffett Foundations.
The Danforth Center invites you to visit its website, , featuring interactive information on the Center scientists, recent news, the 2012 annual report and 鈥淩oots & Shoots鈥� blog that help keep visitors up to date with Center鈥檚 current operations and areas of research. Follow us on Twitter at @DanforthCenter.
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