Browsing by Author "Reichelt, Michael"

Now showing 1 - 6 of 6

The Ca2+ channel CNGC19 regulates Arabidopsis defense against spodoptera herbivory
(American Society of Plant Biologists, 2019) Meena, Mukesh Kumar; Prajapati, Ramgopal; Krishna, Deepthi; Divakaran, Keerthi; Pandey, Yogesh; Reichelt, Michael; Mathew, M.K.; Boland, Wilhelm; Mithöfer, Axel; Vadassery, Jyothilakshmi
Cellular calcium elevation is an important signal used by plants for recognition and signaling of environmental stress. Perception of the generalist insect, Spodoptera litura, by Arabidopsis thaliana activates cytosolic Ca2+ elevation, which triggers downstream defense. However, not all the Ca2+ channels generating the signal have been identified, nor are their modes of action known. We report on a rapidly activated, leaf vasculature- and plasma membrane-localized, CYCLIC NUCLEOTIDE GATED CHANNEL19 (CNGC19), which activates herbivory-induced Ca2+ flux and plant defense. Loss of CNGC19 function results in decreased herbivory defense. The cngc19 mutant shows aberrant and attenuated intra-vascular Ca2+ fluxes. CNGC19 is a Ca2+ permeable channel, as hyperpolarization of CNGC19-expressing Xenopus oocytes in the presence of both cAMP and Ca2+ results in Ca2+ influx. Breakdown of Ca2+-based defence in cngc19 mutants leads to a decrease in herbivory-induced JA-Ile biosynthesis and expression of JA responsive genes. cngc19 mutants are deficient in aliphatic glucosinolate accumulation and hyperaccumulate its precursor, methionine. CNGC19 modulates aliphatic glucosinolate biosynthesis in tandem with BRANCHED-CHAIN AMINO ACID TRANSAMINASE4 (BCAT4), which is involved in the chain elongation pathway of Met-derived glucosinolates. Furthermore, CNGC19 interacts with herbivory-induced CALMODULIN2 (CaM2) in planta. Together, our work reveals a key mechanistic role for the Ca2+ channel CNGC19 in the recognition of herbivory and the activation of defense signaling.
Calmodulin-like protein CML37 is a positive regulator of ABA during drought stress in Arabidopsis
(Taylor & Francis Group, 2015) Scholz, Sandra S; Reichelt, Michael; Vadassery, Jyothilakshmi; Mithöfer, Axel
Plants need to adapt to various stress factors originating from the environment. Signal transduction pathways connecting the recognition of environmental cues and the initiation of appropriate downstream responses in plants often involve intracellular Ca(2+) concentration changes. These changes must be deciphered into specific cellular signals. Calmodulin-like proteins, CMLs, act as Ca(2+) sensors in plants and are known to be involved in various stress reactions. Here, we show that in Arabidopsis 2 different CMLs, AtCML37 and AtCML42 are antagonistically involved in drought stress response. Whereas a CML37 knock-out line, cml37, was highly susceptible to drought stress, CML42 knockout line, cml42, showed no obvious effect compared to wild type (WT) plants. Accordingly, the analysis of the phytohormone abscisic acid (ABA) revealed a significant reduction of ABA upon drought stress in cml37 plants, while in cml42 plants an increase of ABA was detected. Summarizing, our results show that both CML37 and CML42 are involved in drought stress response but show antagonistic effects.
Heterotic patterns of primary and secondary metabolites in the oilseed crop Brassica juncea
(Springer Nature, 2019) Bajpai, Prabodh K.; Reichelt, Michael; Augustine, Rehna; Gershenzon, Jonathan; Bisht, Naveen C.
Heterosis refers to the superior performance of F1 hybrids over their respective parental inbred lines. Although the genetic and expression basis of heterosis have been previously investigated, the metabolic basis for this phenomenon is poorly understood. In a preliminary morphological study in Brassica juncea, we observed significant heterosis at the 50% flowering stage, wherein both the growth and reproduction of F1 reciprocal hybrids were greater than that of their parents. To identify the possible metabolic causes or consequences of this heterosis, we carried out targeted LC-MS analysis of 48 primary (amino acids and sugars) and secondary metabolites (phytohormones, glucosinolates, flavonoids, and phenolic esters) in five developmental tissues at 50% flowering in hybrids and inbred parents. Principal component analysis (PCA) of metabolites clearly separated inbred lines from their hybrids, particularly in the bud tissues. In general, secondary metabolites displayed more negative heterosis values in comparison to primary metabolites. The tested primary and secondary metabolites displayed both additive and non-additive modes of inheritance in F1 hybrids, wherein the number of metabolites showing an additive mode of inheritance were higher in buds and siliques (52.77–97.14%) compared to leaf tissues (47.37–80%). Partial least regression (PLS) analysis further showed that primary metabolites, in general, displayed higher association with morphological parameters in F1 hybrids. Overall, our results are consistent with a resource-cost model for heterosis in B. juncea, where metabolite allocation in hybrids appears to favor growth, at the expense of secondary metabolism.
An LC-MS/MS assay for enzymatic characterization of methylthioalkylmalate synthase (MAMS) involved in glucosinolate biosynthesis
(Elsevier B.V., 2022) Kumar, Roshan; Reichelt, Michael; Bisht, Naveen C.
Brassicaceae are blessed with specialized metabolites called glucosinolates (GSLs), which along with their degradation products, are beneficial in agriculture and human health. To date, more than 130 GSL structures have been identified, mostly derived from the amino acid methionine. The biosynthesis of methionine-derived aliphatic GSLs starts with a side-chain elongation step involving a recursive three-step cyclic process that incorporates a new methylene group into the 2-oxo acid to form a series of elongated 2-oxo acids. Methylthioalkylmalate synthase (MAMS) catalyzes the first committed step in the side-chain elongation of methionine-derived GSLs. The substrate specificity of MAMS with different 2-oxo acids determines whether reaction products of a given cycle enter for an additional round of chain elongation or enter into core GSLs structure formation. Multiple MAMS encoding genes are present in the Brassicaceae species and are known to play a central role in shaping the diverse profile of aliphatic GSLs. We recently established a highly sensitive LC-MS/MS-based methodology that quantifies the MAMS activity by estimating the amount of the next intermediate of the pathway, the 2-malate derivatives. Overall, this chapter describes the protocol for the expression, purification, and steady-state kinetic analysis of the recombinant MAMS protein.
Omega hydroxylated JA-Ile is an endogenous bioactive jasmonate that signals through the canonical jasmonate signaling pathway
(Elsevier B.V., 2019) Jimenez-Aleman, Guillermo H.; Almeida-Trapp, Marilia; Fernández-Barbero, Gemma; Gimenez-Ibanez, Selena; Reichelt, Michael; Vadassery, Jyothilakshmi; Mithöfer, Axel; Caballero, Julio; Boland, Wilhelm; Solano, Roberto
Jasmonates are fatty acid derivatives that control several plant processes including growth, development and defense. Despite the chemical diversity of jasmonates, only jasmonoyl-L-isoleucine (JA-Ile) has been clearly characterized as the endogenous ligand of the jasmonate co-receptors (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-OH-JA-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.
Trichoderma harzianum protects the Arabidopsis salt overly sensitive 1 mutant against salt stress
(Springer Nature Publishing AG, 2025) Gandhi, Akanksha; Reichelt, Michael; Goyal, Divya; Vadassery, Jyothilakshmi; Oelmüller, Ralf
Salt stress is one of the major environmental factors that limits crop productivity. To mount an effective response to cope with salt stress, plants rely on the salt overly sensitive (SOS) pathway. The SOS1, SOS2 and SOS3 proteins are crucial for the maintenance of ion homeostasis and the sos1 mutant is hypersensitive to salt stress. Trichoderma harzianum, a beneficial fungus, increases the tolerance of plants to abiotic stresses. We examined the effect of the Trichoderma strain on the performance of the salt overly sensitive (sos1) mutant of Arabidopsis under salt stress. Compared to the isogenic glabra1 (gl1) control seedlings, the fresh weight, chlorophyll fluorescence, photosynthetic pigment content and transcript level of genes involved in ROS scavenging were increased in Trichoderma-inoculated sos1 plants under 150 mM salt stress. Trichoderma also enhanced the accumulation of the osmolytes proline, alanine, as well as the sucrose and glucose in the salt-stressed sos1, but not gl1 mutants, and the accumulation of Na+ was restricted in the sos1 mutant. The beneficial effects of T. harzianum could be attributed to higher colonization rates of the sos1 mutant compared to the gl1 controls. In conclusion, these findings underscore that the Trichoderma strain activates stronger salt protective responses in the salt-sensitive sos1 mutant than in control gl1 plants. Therefore, the Trichoderma strain is a valuable tool to investigate how a beneficial endophyte can stimulate salt tolerance responses in the host to promote its performance under stress.