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Abstract

Abiotic and biotic environmental stimuli are sensed and transduced by signalling networks in plants leading to an appropriate pattern of protective gene expression.  My lab is interested in how such primary signals are coupled to calcium signals; how the resulting calcium signals are connected to nuclear events in plants; and how calcium, involved in response to so many different primary signals, can encode information to elicit the correct specific gene expression responses.  We are currently researching the following questions:

(1)   How are primary signals coupled to cellular changes in calcium? This question has been very difficult to answer via orthodox pharmacological and genetic approaches. We have therefore started mathematical modelling of calcium responses to low temperature as a test system, aiming to predict early events in cold perception upstream of rapid cellular calcium changes [1].

(2)   How are cellular signals coupled to events in the nucleus leading to changes in gene expression?  We have focussed on identifying calcium-dependent gene regulons in Arabidopsis, and subsequently the promoter motifs and transcription factors (TFs) involved [2]. Amongst these are the CAMTA, CBF/DREB1, AREBP/ABF and TCP TFs. Current work in our lab aims to identify the molecular mechanisms by which calcium regulates these TFs, starting with CAMTAs as models.

(3)   How is specific information regarding the primary signal encoded into calcium responses?  The calcium signature hypothesis states that different external stimulus elicit unique spatiotemporal patterns of elevations in cellular calcium concentration thus encoding stimulus-specific information that is “read” by plants. We have tested this hypothesis using the Arabidopsis transcriptome as a signalling output and we observe that different calcium signatures provoke the expression of largely distinct groups of genes, likely regulated by different transcription factors [3]. By a combination of experimental and mathematical approaches, we have determined how calcium signatures are “decoded” by specific transcription factors to lead to a specific response [4]. Our most recent work has focussed on decoding the calcium signalling involved in the plant immunity response [5].

References

1. Liu, J.L., Knight, H., Hurst, C.H., and Knight, M.R. (2012). Modelling and experimental analysis of the role of interacting cytosolic and vacuolar pools in shaping low temperature calcium signatures in plant cells. Mol Biosyst 8, 2205-2220.
2. Whalley, H.J., Sargeant, A.W., Steele, J.F.C., Lacoere, T., Lamb, R., Saunders, N.J., Knight, H., and Knight, M.R. (2011). Transcriptomic Analysis Reveals Calcium Regulation of Specific Promoter Motifs in Arabidopsis. Plant Cell 23, 4079-4095.
3. Whalley, H.J., and Knight, M.R. (2013). Calcium signatures are decoded by plants to give specific gene responses. New Phytol 197, 690-693.
4. Liu, J.L., Whalley, H.J., and Knight, M.R. (2015). Combining modelling and experimental approaches to explain how calcium signatures are decoded by calmodulin-binding transcription activators (CAMTAs) to produce specific gene expression responses. New Phytol 208, 174-187.
5. Lenzoni, G., Liu, J.L., and Knight, M.R. (2018). Predicting plant immunity gene expression by identifying the decoding mechanism of calcium signatures. New Phytol 217, 1598-1609