title: CML42-mediated calcium signaling coordinates responses to Spodoptera herbivory and abiotic stresses in Arabidopsis.
abstract: In the interaction between Arabidopsis (Arabidopsis thaliana) and the generalist herbivorous insect Spodoptera littoralis, little is known about early events in defense signaling and their link to downstream phytohormone pathways. S. littoralis oral secretions induced both Ca²⁺ and phytohormone elevation in Arabidopsis. Plant gene expression induced by oral secretions revealed up-regulation of a gene encoding a calmodulin-like protein, CML42. Functional analysis of cml42 plants revealed more resistance to herbivory than in the wild type, because caterpillars gain less weight on the mutant, indicating that CML42 negatively regulates plant defense; cml42 also showed increased aliphatic glucosinolate content and hyperactivated transcript accumulation of the jasmonic acid (JA)-responsive genes VSP2 and Thi2.1 upon herbivory, which might contribute to increased resistance. CML42 up-regulation is negatively regulated by the jasmonate receptor Coronatine Insensitive1 (COI1), as loss of functional COI1 resulted in prolonged CML42 activation. CML42 thus acts as a negative regulator of plant defense by decreasing COI1-mediated JA sensitivity and the expression of JA-responsive genes and is independent of herbivory-induced JA biosynthesis. JA-induced Ca²⁺ elevation and root growth inhibition were more sensitive in cml42, also indicating higher JA perception. Our results indicate that CML42 acts as a crucial signaling component connecting Ca²⁺ and JA signaling. CML42 is localized to cytosol and nucleus. CML42 is also involved in abiotic stress responses, as kaempferol glycosides were down-regulated in cml42, and impaired in ultraviolet B resistance. Under drought stress, the level of abscisic acid accumulation was higher in cml42 plants. Thus, CML42 might serve as a Ca²⁺ sensor having multiple functions in insect herbivory defense and abiotic stress responses.
authors.affiliation: Departments of Bioorganic Chemistry , Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
authors.forename: Jyothilakshmi
authors.initials: J
authors.lastname: Vadassery
authors.forename: Michael
authors.initials: M
authors.lastname: Reichelt
authors.forename: Bettina
authors.initials: B
authors.lastname: Hause
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gershenzon
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Boland
authors.forename: Axel
authors.initials: A
authors.lastname: Mithöfer
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000469:parasitology* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005961:Glucosinolates / Q000378:metabolism; D060434:Herbivory / Q000187:drug effects / Q000502:physiology*; D052139:Intracellular Calcium-Sensing Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D054883:Oxylipins / Q000378:metabolism / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D018411:Spodoptera / Q000187:drug effects / Q000502:physiology*; D013312:Stress, Physiological / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C575861:CML42 protein, Arabidopsis; D003517:Cyclopentanes; D005961:Glucosinolates; D052139:Intracellular Calcium-Sensing Proteins; D054883:Oxylipins; D012333:RNA, Messenger; C011006:jasmonic acid; D002118:Calcium