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C4 and crassulacean acid metabolism (CAM) within a single leaf: elucidating the components, plasticity and signaling behind a rare photosynthetic adaptation

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Renata Callegari Ferrari
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
Defense date:
Examining board members:
Luciano Freschi; Danilo da Cruz Centeno; Igor Cesarino; Katia Itzel Silvera
Advisor: Luciano Freschi; James Hartwell

The C4 cycle and crassulacean acid metabolism (CAM) are two common carbon concentrating mechanisms (CCM) in vascular plants. They have biochemical similarities, but represent very different ecological adaptations, as a result of evolutionary, regulatory and structural differences. It was believed they were incompatible to occur in a single organism, but the genus Portulaca challenges this assumption, as it presents intermediate C3-C4 and C4 species capable of switching to CAM according to water availability. However, the genetic and regulatory mechanisms that enable this rare photosynthetic adaptation to occur are still poorly understood. Therefore, the aim of this doctoral thesis was to investigate the C4 to CAM transition in P. oleracea from a physiological and molecular point of view. After a brief introduction to the subject, chapter I contextualizes and proposes the species as a model for studying the C4-CAM transition. Chapter II characterized the central genetic machinery involved in both CCMs in P. oleracea using transcriptome data associated with phylogenetic and physiological analyses. Chapter III explored the morphophysiological plasticity of the species, characterizing CAM in different subspecies originated in different parts of the world. Chapter IV discusses the best optimized molecular strategies and protocols enabling the use of P. oleracea as a C4-CAM model. Finally, Chapter V characterizes the molecular and hormonal signaling during the C4-to-CAM transition and reversion and brings insights into the influence of the circadian clock on both CCMs\' functioning. In general, and most importantly in the global context of climate change, this work aimed to emphasize that C4 and CAM not only represent interesting physiological adaptations from both a functional and evolutionary point of view, but are also important mechanisms for the development of society, as they occur separately in cultivars used in food production and biofuels. Thus, this work provides information that makes it possible to explore the complexity of Portulaca as a blueprint for future development via genetic engineering of cultivars that can intercalate C4 and CAM in a single organism according to the availability of resources in the environment. (AU)

FAPESP's process: 16/04755-4 - Exploring C4 and Crassulacean Acid Metabolism (CAM) compatibility within a single organism: changes in global transcriptional profile, hormonal regulation, and tissue localization of key C4 and CAM components in Portulaca oleracea
Grantee:Renata Callegari Ferrari
Support type: Scholarships in Brazil - Doctorate (Direct)