Phosphorylation of Phosphoenolpyruvate Carboxylase Is Essential for Maximal and Sustained Dark CO2 Fixation and Core Circadian Clock Operation in the Obligate Crassulacean Acid Metabolism Species Kalanchoe fedtschenkoi

Boxall, Susanna F, Dever, Louisa V ORCID: 0000-0001-7801-5622, Knerova, Jana, Gould, Peter D ORCID: 0000-0002-0709-1190 and Hartwell, James ORCID: 0000-0001-5000-223X (2017) Phosphorylation of Phosphoenolpyruvate Carboxylase Is Essential for Maximal and Sustained Dark CO2 Fixation and Core Circadian Clock Operation in the Obligate Crassulacean Acid Metabolism Species Kalanchoe fedtschenkoi. PLANT CELL, 29 (10). pp. 2519-2536.

Text Boxall_et_al_The_Plant_Cell_29_2519_2536.full.pdf - Published version Download (2MB)

Abstract

Phosphoenolpyruvate carboxylase (PPC; EC 4.1.1.31) catalyzes primary nocturnal CO2 fixation in Crassulacean acid metabolism (CAM) species. CAM PPC is regulated posttranslationally by a circadian clock-controlled protein kinase called phosphoenolpyruvate carboxylase kinase (PPCK). PPCK phosphorylates PPC during the dark period, reducing its sensitivity to feedback inhibition by malate and thus enhancing nocturnal CO2 fixation to stored malate. Here, we report the generation and characterization of transgenic RNAi lines of the obligate CAM species Kalanchoë fedtschenkoi with reduced levels of KfPPCK1 transcripts. Plants with reduced or no detectable dark phosphorylation of PPC displayed up to a 66% reduction in total dark period CO2 fixation. These perturbations paralleled reduced malate accumulation at dawn and decreased nocturnal starch turnover. Loss of oscillations in the transcript abundance of KfPPCK1 was accompanied by a loss of oscillations in the transcript abundance of many core circadian clock genes, suggesting that perturbing the only known link between CAM and the circadian clock feeds back to perturb the central circadian clock itself. This work shows that clock control of KfPPCK1 prolongs the activity of PPC throughout the dark period in K. fedtschenkoi, optimizing CAM-associated dark CO2 fixation, malate accumulation, CAM productivity, and core circadian clock robustness.

Item Type:	Article
Uncontrolled Keywords:	Phosphoenolpyruvate Carboxylase, Plant Proteins, Gene Expression Regulation, Plant, Phosphorylation, Circadian Rhythm, Circadian Clocks, Protein Serine-Threonine Kinases
Depositing User:	Symplectic Admin
Date Deposited:	14 Nov 2017 10:58
Last Modified:	19 Jan 2023 06:50
DOI:	10.1105/tpc.17.00301
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3012150