Melatonin functions in priming of stomatal immunity inPanax notoginseng and Arabidopsis thaliana

Abstract

Melatonin plays important roles in plant disease response, but the mechanisms are largely unknown. Here, we show that melatonin functions in stomatal immunity in Panax notoginseng and Arabidopsis (Arabidopsis thaliana). Biochemical analyses showed that melatonin-induced stomatal closure plays a prominent role in preventing invasion of bacteria Pseudomonas syringe pv. tomato (Pst) DC3000 via activation of mitogen-activated protein kinase (MAPK) and NADPH oxidase-mediated reactive oxygen species production in P. notoginseng. Putative phytomelatonin receptor 1 (PMTR1) is a plasma membrane protein required for perceiving melatonin signaling in stomatal closure and activation of MAPK. Biochemical and genetic tests found PMTR1 is essential for flg22- and melatonin-induced MAPK activation in a heterotrimeric GTP-binding protein Gα subunit GPA1-independent manner. GPA1 functions in the same genetic pathways of FLS2/BAK1 (FLAGELLIN SENSING 2/BRASSINOSTEROID INSENSITIVE 1-associated kinase 1)- as well as PMTR1-mediated flg22 and melatonin signaling in stomatal closure. The stomata in pmtr1 are insensitive to melatonin and flg22, but the application of melatonin induces stomatal closure and reduces the bacterial growth in fls2 and bak1 plants, indicating that PMTR1 might be a downstream signaling component in FLS2- and BAK1-mediated stomatal immunity. In summary, our results (i) demonstrate that phytomelatonin functions in priming of stomatal immunity and (ii) provide insights into the phytomelatonin signaling transduction pathway.

Genetic and evolutionary dissection of melatonin response signaling facilitates the regulation of plant growth and stress responses

“…299 PMTR1 could delay flowering time by interacting with GA, SL, and ROS (H 2 O 2 ) signaling pathway. 228 NtMYB10.1 overexpression upregulated JA biosynthetic and signaling genes, as well as NtACO in flowers to promote floral development. 300 A relationship between ROS and HSP also seemed to exist, corroborating the hypothesis that during the course of evolution, plants were able to achieve a high degree of control over ROS toxicity and were now using ROS as signaling molecules to induce HSPs.…”

Phytomelatonin: an emerging new hormone in plants

“…salicylic acid, jasmonates, ABA) and via regulation of expression of genes associated with pathogen responses, disease resistance, and immunity ( Zeng et al , 2022 ). In Panax notoginseng , foliar application of melatonin decreases the incidence of leaf diseases such as grey mould, round spot, and black spot, with phytomelatonin-induced stomatal closure playing a prominent role in preventing bacterial invasion in Arabidopsis and P. notoginseng via PMTR1-medaited activation of the GPA1- and MAPK-signaling pathways, respectively ( Yang et al , 2021 ). It is worth noting that pmtr1 and gpa1 mutants are also insensitive to flg22-induced stomatal closure in Arabidopsis, indicating that PMTR1 is required for FLS1- and BAK1-mediated flg22 signaling in stomata-mediated defence ( Yang et al , 2021 ).…”

The phytomelatonin receptor PMTR1 regulates seed development and germination by modulating abscisic acid homeostasis in Arabidopsis thaliana

“…8 Similar to plant hormones, MLT is involved in a series of possible cellular and physiological actions such as intracellular Ca 2+ oscillations, stomatal movement, seed germination, root morphogenesis, growth, flowering, senescence, circadian rhythms, tropism, photosynthesis, water/CO 2 exchange, plant immunity, and stress responses. [8][9][10][11][12][13][14] The crosstalk between MLT and the classical phytohormones such as auxin, abscisic acid (ABA), gibberellin (GA), cytokinin, salicylic acid (SA), jasmonic acid, ethylene, brassinosteroid (BR), and strigolactone has been documented in numbers of studies. For instance, MLT inhibits seed germination by crosstalk with ABA, GA, and auxin in Arabidopsis.…”