Identification of interacting protein partners of cyclic nucleotide gated channel 19 (CNGC19) and its role in plant defense against herbivory
Student name: Ms Riya Joon
Guide: Dr Ramakrishnan Sitaraman
Year of completion: 2017
Host Organisation: National Institute of Plant Genome Research, New Delhi
Supervisor (Host Organisation): Dr Jyothilakshmi Vadassery
Abstract: Insect herbivore attack is a devastating biotic stress affecting plant productivity. To deal with this stress, plants have developed numerous defense responses that occur at different intervals of time, ranging from seconds to hours. Large amount of research has been carried out on the jasmonate mediated downstream processes that take place upon plant defense against herbivory. However the recognition process in plant-herbivore interactions and the signal transduction pathways connecting it to downstream defense induction are less well understood making it difficult to manipulate genetically. I have used Arabidopsis and its herbivore pest Spodoptera litura (cutworm), a generalist insect, as model system to study how plant defense is activated rapidly upon insect herbivory. A most activated defense response upon stress perception in plants is Ca2+ influx into the cytosol which warns the plant of an impending attack. Ca2+ elevations occur due to opening of ion channels on plasma membrane or intracellular organelles allowing Ca2+ influx into cytosol. In contrast to the response to abiotic stresses and pathogens, the role of Ca2+ as second messenger in plant defense strategies to insect herbivory is not very well understood. To identify the early activated defense genes upon Spodoptera herbivory, a microarray analysis was previously done in the lab. It was found out that CNGC19 is highly expressed in Arabidopsis upon S. litura herbivory. Functional characterization revealed that the CNGC19 gene product positively regulates plant defense against insect herbivore. The CNGC19 protein structure consists of six transmembrane domains (S1-S6) along with a pore domain which is present between S5 and S6, C-terminal cyclic nucleotide monophosphates (cNMPs) binding domain (CNBD) and a calmodulin (CaM))-binding domain. To identify the possible interacting protein partners of CNGC19, we examined calcium sensor proteins (CaMs and CMLs) which might bind to the C- or N-terminal domains of CNGC19. To find out whether these proteins interact with CNGC19, yeast two-hybrid assay (Y2H) was carried out. I have identified from my work that CaM1, CaM2, CaM3, CaM4, CaM6 and CaM7 isoforms of calmodulin and calmodulin-like protein 37 (CML 37) interact with the C-terminus of CNGC19.
Key words: - Plant-insect interaction, Ca2+ signaling, Ca2+ sensor proteins, Cyclic-nucleotide gated channels (CNGCs), Yeast-two hybrid system.
