Publications of NIPGR Scientists

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Author: search.filters.author.Meena, Mukesh KumarSubject: search.filters.subject.Calcium

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    Jasmonic acid (JA) induced-calcium elevation in Arabidopsis is highly variable due to time of day and conversion to JA-Ile
    (Springer Nature Publishing AG, 2020) Prajapati, Ramgopal; Mittal, Deepika; Meena, Mukesh Kumar; Vadassery, Jyothilakshmi
    Plants have evolved mechanisms to effectively anticipate environmental changes via diurnal rhythmicity (day/night) maintained by the circadian clock. Jasmonic acid biosynthesis and signalling are known to be under the control of the circadian clock. Both JA and its bioactive form jasmonoyl-L-isoleucine (JA-Ile) when externally added can induce a cytosolic Ca2? influx in Arabidopsis thaliana. JA and JA-Ile induced Ca2? is poorly understood and often used interchangeably to study Ca2? regulation of jasmonates. We attempted to understand if they are similar and if diurnal rhythms or time of day regulate them. JA induced Cacyt 2? signature is variable according to time-of-day in Arabidopsis. JA is sensed in two ways according to the time-of-day (a) directly sensed as JA and induces Cacyt 2? elevation (b) JA gets converted into the JA-Ile by JAR1 and is sensed as JA-Ile, which we proved using jar1-1*aequorin. This twin sensing mode is responsible for variability in JA induced Cacyt 2? signature. We further suggest caution when using JA as a stimulant for Cacyt 2? elevation measurements to compare wild-type (Col-0 transformed with pMAQ2; transgenic aequorin) and effect of different mutations. On the other hand bioactive JA-Ile induced Cacyt 2? signature is constant diurnally with maximum amplitude at dawn which coincides with maximum sensitivity of JA-Ile receptor, COI1 and increased VSP2 expression. From the above study we conclude that JA-Ile induced Cacyt 2? elevation is a better read-out than the highly variable JA-induced Cacyt 2? elevations to study the output pathways.
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    Decoding and relay of calcium signals by CBL-CIPK module in plants
    (Indian National Science Academy, 2019) Meena, Mukesh Kumar; Sardar, Atish; Chattopadhyay, Debasis
    Calcium is an essential macronutrient and a second messenger for signal transduction in plants. Apart from acting as a second messenger, calcium is also required for cytoskeleton, cell division, pollen tube growth and as a co-factor. Cytoplasmic calcium ion ([Ca2+](cyt)) is maintained at a low level, however, is rapidly elevated using storages in organelles on perception of a stimulus. Ca2+-binding proteins that sense the kinetics and magnitude of elevated [Ca2+](cyt) convert the chemical signals to biological signals and define specificity of responses. These proteins are broadly classified into sensor relays and sensor responders. Sensor relay proteins require another interacting protein to transmit the signal; whereas, the sensor responders combine within one protein the relay, amplification and response functions. A significant achievement has been made in the last three decades that identified and characterized various proteins instrumental in decoding Ca2+-signals in plant cells. The latest addition in Ca2+-signaling is Calcineurin B-like proteins (CBLs) and their interacting kinases (CIPKs). It is believed that flexibility of interactions between different CBL and CIPK proteins and their sub-cellular localizations are crucial in sensing and responding to specific signals. In this review, we have laid emphasis on the recent and emerging advancements in understanding of the CBL-CIPK module.