Muhaidat R, McKown AD, Al Zoubi M, Bani Domi Z, Otoum O. C
4 photosynthesis and transition of Kranz anatomy in cotyledons and leaves of Tetraena simplex.
Am J Bot 2018;
105:822-835. [PMID:
29791720 DOI:
10.1002/ajb2.1087]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 02/22/2018] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY
Tetraena simplex is an independently evolved C4 species in the Zygophylloideae (Zygophyllaceae) and a characteristic forb of saline flats in hot and sandy desert habitats. During early ontogeny, the species had a morphological shift from planar cotyledons (dorsiventral symmetry) to terete, succulent leaves (radial symmetry). We tested whether this shift had a corresponding change in internal Kranz anatomy and tissue patterning.
METHODS
For a comprehensive characterization of C4 photosynthesis across early ontogeny in T. simplex, structural and ultrastructural anatomical properties and localization patterns, activities, and immunoblotting of key C4 photosynthetic enzymes were compared in mesophyll and bundle sheath tissues in cotyledons and leaves.
KEY RESULTS
Cotyledons and leaves possessed different types of Kranz anatomy (atriplicoid type and a "Tetraena" variant of the kochioid type, respectively), reflecting the change in leaf morphology. In bundle sheath cells, key differences in ultrastructural features included increased organelle numbers and chloroplast thylakoid stacking. C4 enzymes had strict tissue-specific localization patterns within bundle sheath and mesophyll cells in both cotyledons and leaves. The decarboxylase NAD-ME maintained the highest activity, increasing from cotyledons to leaves. This classified T. simplex as fully C4 across ontogeny and a strictly NAD-ME biochemical subtype.
CONCLUSIONS
Tetraena simplex cotyledons and leaves showed differences in Kranz type, with associated progression in ultrastructural features, and differing activities/expression levels of C4 enzymes. Furthermore, leaves characterized a new "Tetraena" variation of the kochioid Kranz anatomy.
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