Improved mesophyll–bundle sheath connectivity is achieved via different mechanisms in C 2 vs C 4 Alternanthera
Year: 2026
Type: article
Abstract: Summary Connectivity between mesophyll (M) and bundle sheath (BS) cells must improve during the evolution of C 4 photosynthesis to facilitate large metabolite fluxes between these cell types, but the trait combinations that enhance M–BS connectivity and the points at which these enhancements occur along the C 3 to C 4 evolutionary trajectory remain unknown. We investigated shifts in M–BS connectivity that accompanied photosynthetic diversification within the eudicot genus Alternanthera from the agriculturally important Amaranthaceae family. We combined transmission electron microscope and confocal microscopy to reconstruct three‐dimensional internal leaf structures of C 3 , C 2 , and C 4 Alternanthera species to reveal differences in the M–BS interface and cell‐to‐cell communication capacity. We found that M–BS connectivity increases stepwise from C 3 to C 2 and to C 4 species, but these shifts are achieved via different combinations of underlying traits in C 2 vs C 4 species. Specifically, increases to vein density were unique to C 2 whilst enhancements to BS cell, pit field, and plasmodesmata densities were unique to C 4 Alternanthera species. Both C 2 and C 4 Alternanthera shorten BS cell length, which may facilitate tighter BS packing to enhance M–BS connectivity. Our findings highlight the diverse mechanisms through which photosynthetic innovation can emerge, providing valuable insight for evolutionary biology and agricultural bioengineering efforts.
Source: New Phytologist
DOI: 10.1111/nph.71218
Institution: Lancaster University
Language: English
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $5,790
Funder: Medical Research Council
OpenAlex ID: W7157310098