Unique photosynthetic phenotypes in Portulaca (Portulacaceae): C3-C4 intermediates and NAD-ME C4 species with Pilosoid-type Kranz anatomy.
Portulacaceae is a family that has considerable diversity in photosynthetic phenotypes. It is one of 19 families of terrestrial plants where species having C4 photosynthesis have been found. Most species in Portulaca are in the alternate-leaved (AL) lineage, which includes one clade (Cryptopetala) with taxa lacking C4 photosynthesis and three clades having C4 species (Oleracea, Umbraticola and Pilosa). All three species in the Cryptopetala clade lack Kranz anatomy, the leaves have C3-like carbon isotope composition and they have low levels of C4 cycle enzymes. Anatomical, biochemical and physiological analyses show they are all C3-C4 intermediates. They have intermediate CO2 compensation points, enrichment of organelles in the centripetal position in bundle sheath (BS) cells, with selective localization of glycine decarboxylase in BS mitochondria. In the three C4 clades there are differences in Kranz anatomy types and form of malic enzyme (ME) reported to function in C4 (NAD-ME versus NADP-ME): Oleracea (Atriplicoid, NAD-ME), Umbraticola (Atriplicoid, NADP-ME) and Pilosa (Pilosoid, NADP-ME). Structural and biochemical analyses were performed on Pilosa clade representatives having Pilosoid-type leaf anatomy with Kranz tissue enclosing individual peripheral vascular bundles and water storage in the center of the leaf. In this clade, all species except P. elatior are NADP-ME-type C4 species with grana-deficient BS chloroplasts and grana-enriched M chloroplasts. Surprisingly, P. elatior has BS chloroplasts enriched in grana and NAD-ME-type photosynthesis. The results suggest photosynthetic phenotypes were probably derived from an ancestor with NADP-ME-type C4, with two independent switches to NAD-ME type.
['Voznesenskaya|Elena V|EV|0000-0002-5919-3340', 'Koteyeva|Nuria K|NK|', 'Edwards|Gerald E|GE|', 'Ocampo|Gilberto|G|']
D005075:Biological Evolution D015153:Blotting, Western D002245:Carbon Dioxide D002247:Carbon Isotopes D018548:Cotyledon D050841:Glycine Dehydrogenase (Decarboxylating) D008291:Malate Dehydrogenase D046529:Microscopy, Electron, Transmission D009243:NAD D010641:Phenotype D010788:Photosynthesis D018515:Plant Leaves D031822:Portulaca
Portulaca C3-C4 intermediate NAD-ME type C3 plants C4 plants NADP-ME type Portulacaceae. chloroplast ultrastructure immunolocalization photosynthetic enzymes