Abstract
Background and AimsCultured cell suspensions have been the preferred model to study the apoplast as well as to monitor metabolic and cell cycle-related changes. Previous work showed that methyl jasmonate (MeJA) inhibits leaf growth in a CORONATINE INSENSITIVE 1 (COI1)-dependent manner, with COI1 being the jasmonate (JA) receptor. Here, the effect of COI1 overexpression on the growth of stably transformed arabidopsis cell cultures is described.MethodsTime-course experiments were carried out to analyse gene expression, and protein and metabolite levels.Key ResultsBoth MeJA treatment and the overexpression of COI1 modify growth, by altering cell proliferation and expansion. DNA content as well as transcript patterns of cell cycle and cell wall remodelling markers were altered. COI1 overexpression also increases the protein levels of OLIGOGALACTURONIDE OXIDASE 1, BETA-GLUCOSIDASE/ENDOGLUCANASES and POLYGALACTURONASE INHIBITING PROTEIN2, reinforcing the role of COI1 in mediating defence responses and highlighting a link between cell wall loosening and growth regulation. Moreover, changes in the levels of the primary metabolites alanine, serine and succinic acid of MeJA-treated Arabidopsis cell cultures were observed. In addition, COI1 overexpression positively affects the availability of metabolites such as β-alanine, threonic acid, putrescine, glucose and myo-inositol, thereby providing a connection between JA-inhibited growth and stress responses.ConclusionsThis study contributes to the understanding of the regulation of growth and the production of metabolic resources by JAs and COI1. This will have important implications in dissecting the complex relationships between hormonal and cell wall signalling in plants. The work also provides tools to uncover novel mechanisms co-ordinating cell division and post-mitotic cell expansion in the absence of organ developmental control.
Highlights
IntroductionJasmonate (JA) signalling, perceived by the CORONATINE INSENSITIVE 1 (COI1) receptor (Chini et al, 2007; Thines et al, 2007; Fonseca et al, 2009; Yan et al, 2009), regulates developmental, abiotic and biotic stresses that among others, involve the cell wall (Balbi and Devoto, 2008; Howe and Jander, 2008; Gális et al, 2009; Wu and Baldwin, 2010; Denness et al, 2011; Noir et al, 2013; Wasternack and Hause, 2013)
Ectopic expression of the CORONATINE INSENSITIVE 1 (COI1)::HA protein was confirmed in both COV1 and COV2 cell cultures by immunodetection using an HA-specific antibody
At 4 days after sub-culturing (DASU), the relative cell number of the Landsberg erecta (Ler) culture was reduced by about 36 %, whereas the JA receptor-overexpressing COV1 and COV2 cultures showed an approx. 39 % and approx. 69 % decrease, respectively (Fig. 2)
Summary
Jasmonate (JA) signalling, perceived by the CORONATINE INSENSITIVE 1 (COI1) receptor (Chini et al, 2007; Thines et al, 2007; Fonseca et al, 2009; Yan et al, 2009), regulates developmental, abiotic and biotic stresses that among others, involve the cell wall (Balbi and Devoto, 2008; Howe and Jander, 2008; Gális et al, 2009; Wu and Baldwin, 2010; Denness et al, 2011; Noir et al, 2013; Wasternack and Hause, 2013). The plant cell wall is a highly dynamic structure and an essential component involved in cell morphogenesis and plant–pathogen interactions (Cosgrove, 2005; Hématy et al, 2009; Szymanski and Cosgrove, 2009). Phytohormones such as abscisic acid (ABA), salicylic acid (SA), JAs and ethylene, as well as reactive oxygen species (ROS) regulate the cross-talk between biotic and abiotic stress responses (reviewed by Fujita et al, 2006; Bolwell and Daudi, 2009). ROS- and JA-dependent processes regulate lignin biosynthesis following damage O’Brien et al (2012) showed, using arabidopsis cell suspension cultures, that the cell wall peroxidase genes PRX33 and PRX34 are required for microbeassociated molecular pattern (MAMP)-activated responses
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