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 (Arabidopsis thaliana) activates cytosolic Ca 21 elevation, which triggers downstream defense. However, not all the Ca 21 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 Ca 21 flux and plant defense. Loss of CNGC19 function results in decreased herbivory defense. The cngc19 mutant shows aberrant and attenuated intravascular Ca 21 fluxes. CNGC19 is a Ca 21-permeable channel, as hyperpolarization of CNGC19-expressing Xenopus oocytes in the presence of both cyclic adenosine monophosphate and Ca 21 results in Ca 21 influx. Breakdown of Ca 21-based defense in cngc19 mutants leads to a decrease in herbivory-induced jasmonoyl-l-isoleucine biosynthesis and expression of JA responsive genes. The 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, which is involved in the chain elongation pathway of Met-derived glucosinolates. Furthermore, CNGC19 interacts with herbivory-induced CALMODULIN2 in planta. Together, our work reveals a key mechanistic role for the Ca 21 channel CNGC19 in the recognition of herbivory and the activation of defense signaling.
Peroxidases have ability to catalyze redox reaction of a wide range of phenolic as well as non-phenolic compounds and exhibited various physiological roles in plant life cycle. From the point of view of industrial applications of peroxidases, the isolation and characterization of peroxidases offering resistance to higher pH and temperature, salts, organic solvents is highly desirable. In this direction, a partial cDNA clone of peroxidase from lemon was isolated and characterized. The peroxidase was found to be defense associated as evident by the higher expression in diseased condition than that of healthy one at both the transcript and enzymatic activity levels. This defense related peroxidase from lemon leaves was purified to homogeneity using quick two step processes of heat treatment and affinity chromatography. The native peroxidase was found to be a heterotrimer of 200 kDa, consisting of two subunits each of 66 kDa while, one subunit of 70 kDa. The purified peroxidase was found to be stable towards heat (retained 92% activity at 80°C for 1 h) and organic solvents, namely ethanol, methanol and isopropanol (retained 30-50% activity in the presence of 50% (v/v) of these solvents for 1 h). Purified peroxidase also exhibited tolerance to heavy metal ions such as Cd 2+ , Ni 2+ and Cs 2+ . The purified lemon peroxidase was found to efficiently oxidize the industrial dyes in the order of aniline blue>methyl orange> indigo carmine >trypan blue > crystal violet, such that 40-54% dye decolorization was observed within 4 h. Thus, the properties exhibited by purified lemon peroxidase make it a promising candidate enzyme for industrial exploitation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.