Open questions on facultative C4-CAM photosynthesis in Portulaca
Callegari Ferrari, Renata (LMU München. Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität und Evolution der Pflanzen)
Reyna-Llorens, Ivan (Centre de Recerca en Agrigenòmica)

Fecha:	2026
Resumen:	Plants have evolved carbon concentrating mechanisms (CCMs) to optimize carbon fixation under environmental conditions that increase photorespiratory and transpiration rates. C4 and CAM photosynthesis are the two most widespread CCM examples across land plants and were typically considered to be incompatible due to biochemical, anatomical, evolutionary, and regulatory characteristics. However, Portulaca oleracea (purslane) was the first reported case to challenge this assumption more than 40 years ago. Although it remains as one of the most characterized C4-CAM species, many aspects of this dual system are still unresolved. This expert review summarizes recent advances in understanding C4-CAM integration in Portulaca, highlighting key genomic, transcriptomic, biochemical and physiological insights, and outlines the most pressing questions about the functioning and evolution of this combined CCM. Future directions for explaining how these convergent pathways emerged in the same lineage include functional studies on key regulatory elements, spatially resolved analyses for protein distribution and metabolic fluxes across leaves, an updated phylogeny of the family, and the integration of molecular and physiological data. So far, it is evident that expressing a weak CAM cycle in a C4 crop might be possible and could entail increased survival, possibly contributing to higher productivity in a future with climate change.
Ayudas:	Agencia Estatal de Investigación PID2022-142613NA-I00
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió acceptada per publicar
Materia:	C4 photosynthesis ; Crassulacean acid metabolism ; Facultative CAM ; Portulaca oleracea ; Carbon concentrating mechanism ; Abiotic stress ; Drought stress ; Phosphoenolpyruvate carboxylase ; Photosynthesis ; PEPC
Publicado en:	Journal of experimental botany, April 2026, art. erag161, ISSN 1460-2431

DOI: 10.1093/jxb/erag161

Postprint 27 p, 749.5 KB

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