Abstract
The proportion of starch, protein and oil in legume seeds is species dependent. The model legume, Medicago truncatula, has predominantly oil and protein stores. To investigate the regulation of seed oil production we compared M. truncatula with M. orbicularis, which has less oil and protein. The types of protein and fatty acids are similar between the two species. Electron microscopy indicated that the size and distribution of the oil bodies in M. orbicularis, is consistent with reduced oil production. M. orbicularis has more extruded endosperm mucilage compared to M. truncatula. The cotyledons have a greater cell wall content, visualized as thicker cell walls. The reduced oil content in M. orbicularis is associated with increased expression of the MtGLABRA2-like (MtGL2) transcription factor, linked to an inverse relationship between mucilage and oil content in Arabidopsis. The expression of the pectin biosynthesis GALACTURONOSYLTRANSFERASE (GAUT) genes, is also increased in M. orbicularis. These increases in extruded mucilage and cell wall storage components in M. orbicularis are accompanied by reduced expression of transcriptional regulators of oil biosynthesis, MtLEAFY COTYLEDON1-LIKE (MtL1L), MtABSCISIC ACID-INSENSITIVE3 (MtABI3), and MtWRINKLED-like (MtWRI), in M. orbicularis. The reduced oil in M. orbicularis, is consistent with increased synthesis of cell wall polysaccharides and decreased expression of master transcription factors regulating oil biosynthesis and embryo maturation. Comparative investigations between these two Medicago species is a useful system to investigate the regulation of oil content and carbon partitioning in legumes.
Highlights
Legumes are the third largest family of flowering plants (Doyle and Luckow, 2003; Gepts et al, 2005) and the second most important crop family with approximately 20,000 species (Doyle and Luckow, 2003; Gepts et al, 2005), representing a significant source of protein and oil for the human diet, animal feedstock and industrial use
Given the thicker cotyledon storage cell walls and extruded mucilage derived from the endosperm cell walls of M. orbicularis (Figures 4A–D, 6, 7); we investigated whether the increased mucilage and cell wall material could be related to changes in the expression of genes potentially involved in the regulation of mucilage biosynthesis and cell wall pectin biosynthesis
Given the increased cell wall material and the thicker cell walls in the M. orbicularis cotyledons, we investigated the expression of GALACTURONOSYLTRANSFERASES (GAUTs) involved in the biosynthesis of the homogalacturonan pectin polysaccharide (Doong and Mohnen, 1998; Atmodjo et al, 2011), potentially a cell wall storage polysaccharide
Summary
Legumes are the third largest family of flowering plants (Doyle and Luckow, 2003; Gepts et al, 2005) and the second most important crop family with approximately 20,000 species (Doyle and Luckow, 2003; Gepts et al, 2005), representing a significant source of protein and oil for the human diet, animal feedstock and industrial use. There has been a substantive focus on the improvement of seed protein quality (Molvig et al, 1997; Wang et al, 2003; Krishnan, 2005). There has been a focus on sugar metabolism in non-oil storage legumes such as Vicia (Weber et al, 2005), the genetic modification of fatty acids and strategies to increase seed oil content in soybean (Clemente and Cahoon, 2009; Roesler et al, 2016). There is a need for more information on the cellular and genetic basis that underlies oil body formation during legume seed development (Repetto and Gallardo, 2012; Wang et al, 2012; Song et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
