Constitutive or seed‐specific overexpression of Arabidopsis G‐protein γ subunit 3 (AGG3) results in increased seed and oil production and improved stress tolerance in Camelina sativa

Abstract

SummaryHeterotrimeric G-proteins consisting of Ga, Gb and Gc subunits play an integral role in mediating multiple signalling pathways in plants. A novel, recently identified plant-specific Gc protein, AGG3, has been proposed to be an important regulator of organ size and mediator of stress responses in Arabidopsis, whereas its potential homologs in rice are major quantitative trait loci for seed size and panicle branching. To evaluate the role of AGG3 towards seed and oil yield improvement, the gene was overexpressed in Camelina sativa, an oilseed crop of the Brassicaceae family. Analysis of multiple homozygous T4 transgenic Camelina lines showed that constitutive overexpression of AGG3 resulted in faster vegetative as well as reproductive growth accompanied by an increase in photosynthetic efficiency. Moreover, when expressed constitutively or specifically in seed tissue, AGG3 was found to increase seed size, seed mass and seed number per plant by 15%-40%, effectively resulting in significantly higher oil yield per plant. AGG3 overexpressing Camelina plants also exhibited improved stress tolerance. These observations draw a strong link between the roles of AGG3 in regulating two critical yield parameters, seed traits and plant stress responses, and reveal an effective biotechnological tool to dramatically increase yield in agricultural crops.

The role of PLDα1 in providing specificity to signal‐response coupling by heterotrimeric G‐protein components in Arabidopsis

“…The existence of a relatively simple repertoire of heterotrimeric G-protein components in plants, combined with their involvement in the regulation of a multitude of physiological responses, has always been perplexing. One canonical and three extra-large Ga, 1 Gb and 3 Gc proteins of Arabidopsis have been shown to affect seed development and germination, meristem development, leaf shape and size, silique development, stomatal physiology and development, modulation of multiple hormone responses, regulation of plants responses to bacterial and fungal pathogens, water and nutrient use efficiency and overall plant architecture, essentially affecting every aspect of plant growth and development (Ullah et al, 2002(Ullah et al, , 2003Chen et al, 2006;Pandey et al, 2006Pandey et al, , 2010Trusov et al, 2006Trusov et al, , 2007Trusov et al, , 2009Warpeha et al, 2006Warpeha et al, , 2007Fan et al, 2008;Nilson and Assmann, 2010a,b;Alvarez et al, 2011;Zhang et al, 2011;Torres et al, 2013;Roy Choudhury et al, 2014;Urano and Jones, 2014;Chakravorty et al, 2015;Maruta et al, 2015). It is generally presumed that the specificity of signalresponse coupling is achieved downstream of the heterotrimer, where the active proteins interact with unique effector proteins, depending on specific signal, tissue type or the developmental stage of the plant.…”

“…Heterotrimeric G-protein complex-mediated signaling pathways are critical for normal growth and development in all eukaryotes. In plants, the role of G-proteins has been established in regulating key developmental and signaling responses that have a profound effect on their architecture, biotic and abiotic stress responses and yield potential, although the repertoire of G-proteins is significantly limited in plants compared with that in metazoan systems Pandey et al, 2006;Trusov et al, 2006;Fan et al, 2008;Warpeha et al, 2008;Liu et al, 2013;Colaneri and Jones, 2014;Roy Choudhury et al, 2014;Urano and Jones, 2014). One canonical and three extralarge Ga, 1 Gb and 3 Gc proteins constitute the core of heterotrimeric G-protein complex in Arabidopsis (Chakravorty et al, 2015;Maruta et al, 2015), compared with the 23 Ga, 5 Gb and 12 Gc proteins that exist in humans.…”

Mutation of RGG2, which encodes a type B heterotrimeric G protein γ subunit, increases grain size and yield production in rice

“…AGG3 was the last identified G γ subunit in Arabidopsis, and it has been reported to affect guard cell K + channels, morphological development and abscisic acid (ABA) responses (Chakravorty et al ., ). Constitutive expression of AGG3 increases organ size in Arabidopsis (Li et al ., ), enhances oil production in Camelina sativa (Roy Choudhury et al ., ) and promotes yield and stress responses in Setaria viridis (Kaur et al ., ). The phenotype of the Arabidopsis G γ triple mutant ( agg1agg2agg3 ) mimics that of agb1 , suggesting that all the members of the G protein family have been discovered in Arabidopsis (Thung et al ., ).…”

Production of mono- and sesquiterpenes in Camelina sativa oilseed

“…Camelina is genetically similar to the model dicot Arabidopsis thaliana (Arabidopsis) and is likewise genetically transformed by the facile floral dip method (Lu and Kang 2008). Previous bioengineering attempts of camelina primarily targeted optimization of oil composition (Lu and Kang 2008;Li et al 2014;Snapp et al 2014;Nguyen et al 2015) and plant morphology (Zhang et al 2012;Lee et al 2014;Roy Choudhury et al 2014). To our knowledge, no study reports refactoring of camelina for the production of terpenes-the largest group of natural compounds.…”