Keywords
Herbivory · Calcium signalling · Ca
2+ -binding proteins · Ca
2+ channels CDPKs ·
Plant defence
16.1 Introduction
Plants encounter herbivores very often in their life span, and this interaction is
continuous since millions of years ago. The myriad of interactions between them
are so unique and specific that they are evolving their mutualism as well as defence
mechanism simultaneously. To deal with insect attack, plants have developed highly
specific defence strategies that include both constitutive as well as inducible means.
Constitutive defence mechanism includes preformed barriers such as cuticle,
trichomes, spines, defensive metabolites, etc., whereas induced plant defence
involves cell wall reinforcement, enhanced synthesis of insecticidal/insect deterrent
proteins and secondary metabolites, etc. Induced defence is cost effective and is
achieved by induction of elaborate defence signalling pathways. During plant–
herbivore interactions, certain consecutive events are detected such as membrane
depolarization, V m changes, elevation in cytoplasmic Ca
2+ levels, and generation of
reactive oxygen species (ROS) (Aldon et al. 2018; Erb and Reymond 2019). Further,
kinases are activated and biosynthesis of phytohormones [Jasmonic Acid (JA),
Salicylic acid (SA), Ethylene (ET)] is upregulated, followed by transcriptional,
proteomic, and metabolic changes (Singh et al. 2008, 2018, 2020). These events
are highly regulated and coordinated by chemical signals.
Among signalling molecules, calcium (Ca
2+ ) is small sized, versatile entity that
participates in the transfer of signals during biotic and abiotic stresses in plants.
Hence Ca
2+ is also known as the universal second messenger or universal signalling
molecule (Song et al. 2008; Batistič and Kudla 2012; Cheval et al. 2013; Moreno
et al. 2014). Ca
2+ is the most frequent and successfully studied molecule during
plant–herbivore interaction. V m polarization and elevation in (Ca
2+ ) cyt occurs within
seconds upon environmental stress. It relays the information intracellularly as well as
intercellularly. In plants Ca
2+ is stored in various organelles and subcellular
compartments, which is released during stress via specific Ca
2+ channels/pumps.
Influx and efflux of Ca
2+ is mediated by specific channels and pumps such as Ca
2+ -
ATPases and H
+ /Ca
2 . In normal cells, higher amount of stored Ca
2+ is found in
apoplast, mitochondria, endoplasmic reticulum, and vacuole in mM range (~1 mM),
whereas its lower levels are maintained in cytosol (100–200 nM) (~0.0001 mM)
(Dodd et al. 2010; Lecourieux et al. 2006). This high concentration of Ca
2+ in the
apoplast is necessary to maintain in order to notice the warning signal of environmental stress conditions. Any deviation from this Ca
2+ concentration is recognized
as stress in plant cells. In response to stress, the Ca
2+ levels in cells change
completely and it increases up to μM range in the cytosol (Messerli et al. 2006).
During herbivory, as soon as the “enemy” starts scrawling and causes damage to
plants, herbivory-specific/ -induced stimulus (HAMPs, DAMPs, and SDSs) is
492
A. Kumar et al.
Herbivory · Calcium signalling · Ca
2+ -binding proteins · Ca
2+ channels CDPKs ·
Plant defence
16.1 Introduction
Plants encounter herbivores very often in their life span, and this interaction is
continuous since millions of years ago. The myriad of interactions between them
are so unique and specific that they are evolving their mutualism as well as defence
mechanism simultaneously. To deal with insect attack, plants have developed highly
specific defence strategies that include both constitutive as well as inducible means.
Constitutive defence mechanism includes preformed barriers such as cuticle,
trichomes, spines, defensive metabolites, etc., whereas induced plant defence
involves cell wall reinforcement, enhanced synthesis of insecticidal/insect deterrent
proteins and secondary metabolites, etc. Induced defence is cost effective and is
achieved by induction of elaborate defence signalling pathways. During plant–
herbivore interactions, certain consecutive events are detected such as membrane
depolarization, V m changes, elevation in cytoplasmic Ca
2+ levels, and generation of
reactive oxygen species (ROS) (Aldon et al. 2018; Erb and Reymond 2019). Further,
kinases are activated and biosynthesis of phytohormones [Jasmonic Acid (JA),
Salicylic acid (SA), Ethylene (ET)] is upregulated, followed by transcriptional,
proteomic, and metabolic changes (Singh et al. 2008, 2018, 2020). These events
are highly regulated and coordinated by chemical signals.
Among signalling molecules, calcium (Ca
2+ ) is small sized, versatile entity that
participates in the transfer of signals during biotic and abiotic stresses in plants.
Hence Ca
2+ is also known as the universal second messenger or universal signalling
molecule (Song et al. 2008; Batistič and Kudla 2012; Cheval et al. 2013; Moreno
et al. 2014). Ca
2+ is the most frequent and successfully studied molecule during
plant–herbivore interaction. V m polarization and elevation in (Ca
2+ ) cyt occurs within
seconds upon environmental stress. It relays the information intracellularly as well as
intercellularly. In plants Ca
2+ is stored in various organelles and subcellular
compartments, which is released during stress via specific Ca
2+ channels/pumps.
Influx and efflux of Ca
2+ is mediated by specific channels and pumps such as Ca
2+ -
ATPases and H
+ /Ca
2 . In normal cells, higher amount of stored Ca
2+ is found in
apoplast, mitochondria, endoplasmic reticulum, and vacuole in mM range (~1 mM),
whereas its lower levels are maintained in cytosol (100–200 nM) (~0.0001 mM)
(Dodd et al. 2010; Lecourieux et al. 2006). This high concentration of Ca
2+ in the
apoplast is necessary to maintain in order to notice the warning signal of environmental stress conditions. Any deviation from this Ca
2+ concentration is recognized
as stress in plant cells. In response to stress, the Ca
2+ levels in cells change
completely and it increases up to μM range in the cytosol (Messerli et al. 2006).
During herbivory, as soon as the “enemy” starts scrawling and causes damage to
plants, herbivory-specific/ -induced stimulus (HAMPs, DAMPs, and SDSs) is
492
A. Kumar et al.