The Circadian Clock in CAM Plants

A circadian clock optimizes many aspects of plant biology relative to the light/dark cycle. One example is the circadian control of primary metabolism and CO2 fixation in plants that carry out a metabolic adaptation of photosynthesis called CAM (crassulacean acid metabolism). These plants perform primary CO2 fixation at night using the enzyme phosphoenolpyruvate carboxylase and exhibit a robust rhythm of CO2 fixation under constant conditions. Transcriptomic analysis has revealed that many genes encoding enzymes in primary metabolic pathways such as glycolysis and starch metabolism are under the control of the circadian clock in CAM plants. These transcript changes are accompanied by changes in metabolite levels associated with flux through these pathways. The molecular basis for the circadian control of CAM remains to be elucidated. Current research is focusing on the identity of the CAM central oscillator and the output pathway that links the central oscillator to the control of plant metabolism.

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The Circadian Clock in CAM Plants

Annual Plant Reviews online ◽

10.1002/9781119312994.apr0214 ◽

2018 ◽

pp. 211-236 ◽

Cited By ~ 1

Author(s):

James Hartwell

Keyword(s):

Circadian Clock ◽

Cam Plants

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Transcriptome and Degradome Profiling Reveals a Role of miR530 in the Circadian Regulation of Gene Expression in Kalanchoë marnieriana

Cells ◽

10.3390/cells10061526 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1526

Author(s):

Zhikang Hu ◽

Ziyan Nie ◽

Chao Yan ◽

Hu Huang ◽

Xianjin Ma ◽

...

Keyword(s):

Gene Expression ◽

Circadian Clock ◽

Regulation Of Gene Expression ◽

Cam Plants ◽

Mirna Genes ◽

Differentially Expressed Mirnas ◽

Transcription Regulators ◽

Cam Species ◽

Encoding Genes

Crassulacean acid metabolism (CAM) is an important photosynthetic pathway for plant adaptation to dry environments. CAM plants feature a coordinated interaction between mesophyll and epidermis functions that involves refined regulations of gene expression. Plant microRNAs (miRNAs) are crucial post-transcription regulators of gene expression, however, their roles underlying the CAM pathway remain poorly investigated. Here, we present a study characterizing the expression of miRNAs in an obligate CAM species Kalanchoë marnieriana. Through sequencing of transcriptome and degradome in mesophyll and epidermal tissues under the drought treatments, we identified differentially expressed miRNAs that were potentially involved in the regulation of CAM. In total, we obtained 84 miRNA genes, and eight of them were determined to be Kalanchoë-specific miRNAs. It is widely accepted that CAM pathway is regulated by circadian clock. We showed that miR530 was substantially downregulated in epidermal peels under drought conditions; miR530 targeted two tandem zinc knuckle/PLU3 domain encoding genes (TZPs) that were potentially involved in light signaling and circadian clock pathways. Our work suggests that the miR530-TZPs module might play a role of regulating CAM-related gene expression in Kalanchoë.

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Inference of Gene Regulatory Network Uncovers the Linkage Between Circadian Clock and Crassulacean Acid Metabolism in Kalanchoë fedtschenkoi

10.1101/745893 ◽

2019 ◽

Author(s):

Robert C. Moseley ◽

Francis Motta ◽

Gerald A. Tuskan ◽

Steve Haase ◽

Xiaohan Yang

Keyword(s):

Gene Expression ◽

Circadian Clock ◽

Gene Regulatory Network ◽

Regulatory Network ◽

Crassulacean Acid Metabolism ◽

Acid Metabolism ◽

Clock Genes ◽

Specific Gene ◽

Cam Plants ◽

Gene Regulatory

AbstractThe circadian clock drives time-specific gene expression, allowing for associated biological processes to be active during certain times of the 24 h day. Crassulacean acid metabolism (CAM) photosynthetic plants represent an interesting case of circadian regulation of gene expression as CO2 fixation and stomatal movement in CAM plants display strong circadian dynamics. The molecular mechanisms behind how the circadian clock enabled these physiological differences is not well understood. Therefore, we set out to investigate whether core circadian elements in CAM plants were re-phased during evolution, or whether networks of phase-specific genes were simply connected to different core elements. We utilized a new metric for identifying candidate core genes of a periodic gene network and then applied the Local Edge Machine (LEM) algorithm to infer regulatory relationships between the candidate core clock genes and orthologs of known core clock genes in K. fedtschenkoi. We also used LEM to identify stomata-related gene targets for K. fedtschenkoi core clock genes and constructed a subsequent gene regulatory network. Our results provide new insights into the mechanism of circadian control of CAM-related genes in K. fedtschenkoi, facilitating the engineering of CAM machinery into non-CAM plants for sustainable crop production in water-limited environments.

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Inference of Gene Regulatory Network Uncovers the Linkage between Circadian Clock and Crassulacean Acid Metabolism in Kalanchoë fedtschenkoi

Cells ◽

10.3390/cells10092217 ◽

2021 ◽

Vol 10 (9) ◽

pp. 2217

Author(s):

Robert C. Moseley ◽

Francis Motta ◽

Gerald A. Tuskan ◽

Steven B. Haase ◽

Xiaohan Yang

Keyword(s):

Gene Expression ◽

Circadian Clock ◽

Gene Regulatory Network ◽

Regulatory Network ◽

Crassulacean Acid Metabolism ◽

Acid Metabolism ◽

Clock Genes ◽

Stomatal Movement ◽

Cam Plants ◽

Gene Regulatory

The circadian clock drives time-specific gene expression, enabling biological processes to be temporally controlled. Plants that conduct crassulacean acid metabolism (CAM) photosynthesis represent an interesting case of circadian regulation of gene expression as stomatal movement is temporally inverted relative to stomatal movement in C3 plants. The mechanisms behind how the circadian clock enabled physiological differences at the molecular level is not well understood. Recently, the rescheduling of gene expression was reported as a mechanism to explain how CAM evolved from C3. Therefore, we investigated whether core circadian clock genes in CAM plants were re-phased during evolution, or whether networks of phase-specific genes were simply re-wired to different core clock genes. We identified candidate core clock genes based on gene expression features and then applied the Local Edge Machine (LEM) algorithm to infer regulatory relationships between this new set of core candidates and known core clock genes in Kalanchoë fedtschenkoi. We further inferred stomata-related gene targets for known and candidate core clock genes and constructed a gene regulatory network for core clock and stomata-related genes. Our results provide new insight into the mechanism of circadian control of CAM-related genes in K. fedtschenkoi, facilitating the engineering of CAM machinery into non-CAM plants for sustainable crop production in water-limited environments.

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