学术活动
学术活动

植物科学前沿系列讲座

2019-10-28

PSC Frontier Seminar series
 
Title 1: When Chemistry meets Biology: identification of a novel OPR3-independent pathway for JA biosynthesis
Speaker: Prof. Andrea Chini, Department of Plant Molecular Genetics, National Centre for Biotechnology, Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
Time: 2:00 pm
Day/Date: November 1st, 2019 (Friday)
Host: Prof. Alberto Macho & Prof. Rosa Lozano-Duran
Venue: PSC Auditorium
 
Abstract
Biosynthesis of the phytohormone jasmonoyl-isoleucine (JA-Ile) requires reduction of the JA precursor 12-oxo-phytodienoic acid (OPDA) by OPDA reductase 3 (OPR3). Previous analyses of the opr3-1 Arabidopsis mutant suggested an OPDA signaling role independent of JA-Ile and its receptor COI1; however, this hypothesis has been challenged because opr3-1 is a conditional allele not completely impaired in JA-Ile biosynthesis. To clarify the role of OPR3 and OPDA in JA-independent defenses, we isolated and characterized a loss-of-function opr3-3 allele.Strikingly, opr3-3 plants remained resistant to necrotrophic pathogens and insect feeding, and activated COI1-dependent JA-mediated gene expression. Analysis of OPDA derivatives identified 4,5-didehydro-JA in wounded wild-type and opr3-3 plants. OPR2 was found to reduce 4,5-didehydro-JA to JA, explaining the accumulation of JA-Ile and activation of JA-Ile-responses in opr3-3 mutants. Our results demonstrate that in the absence of OPR3, OPDA enters the β-oxidation pathway to produce 4,5-ddh-JA as a direct precursor of JA and JA-Ile, thus identifying an OPR3-independent pathway for JA biosynthesis.We are also addressing the biological relevance of this novel pathway. Our recent results suggest that this pathway is the original/ancestral pathway for biosynthesis of JA and dn-OPDA that possibly evolved in algae and is the predecessor of the OPR3-dependent pathway in vascular plants.
 
Title 2: Omega hydroxylated JA-Ile is an endogenous bioactive jasmonate.
Speaker: Dr. Guillermo H. Jimenez-Aleman, Department of Plant Molecular Genetics, National Centre for Biotechnology, Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
Time: 2:45 pm
Day/Date: November 1st, 2019 (Friday)
Host: Prof. Alberto Macho & Prof. Rosa Lozano-Duran
Venue: PSC Auditorium
 
Abstract
Jasmonates are fatty acid derivatives that control several plant processes including growth, development and defense. Despite the chemical diversity of jasmonates, only jasmonoyl-Lisoleucine (JA-Ile) has been clearly characterized as the endogenous ligand of the jasmonate coreceptors (COI1-JAZs) in higher plants. Currently, it is accepted that ω-hydroxylation of JA-Ile leads to inactivation of the molecule. This study shows that ω-hydroxylated JA-Ile (12-OH-JA-Ile) retains bioactivity and signals through the canonical JA-pathway. The results suggest that 12-OHJA-Ile differentially activates a subset of JA-Ile co-receptors that may control and/or modulate particular jasmonate dependent responses. It is proposed that after a strong immune response mediated by JA-Ile, the ω-hydroxylated form modulates JA-Ile activated processes thereby improving plant resilience.
The seminars will be delivered in English.