Camo-Escobar, D. | bioRxiv Science

bioRxiv2026

The genetic architecture of leaf vein density traits and its importance for photosynthesis in maize

O_LILeaf venation density has significantly increased during plant evolution. Higher densities are observed in angiosperms compared to early land plants, and among angiosperms, recently diverged C4 species have the highest values. This has allowed leaves to increase water conductance, transpiration and possibly photosynthesis. Despite its importance, the genetic architecture of this trait is not well characterized and its relationship with photosynthesis has not been clearly established. C_LIO_LIUsing native Mexican varieties of maize adapted to a wide range of environmental conditions, we show that vein density is variable and plastic. We leverage this variation to perform correlation analyses with photosynthetic rates and to map genetic regions associated with vein patterning traits using a MAGIC population. C_LIO_LIOur results show that higher vein densities are correlated with higher photosynthetic rates, but only for small intermediate veins. Varieties adapted to drier environments can substantially increase vein density in response to heat, suggesting a role in water use efficiency. We further detected 12 QTLs associated with vein patterning and identified candidate genes related to small intermediate vein development. C_LIO_LIThese findings have implications for understanding vein architecture evolution, particularly that of C4 plants, which have significantly higher photosynthetic efficiency and productivity under warm and dry conditions. C_LI

plant biology↗

bioRxiv2023

A common regulatory switch controls a suite of C4 traits in multiple cell types

The C4 photosynthetic pathway provided a major advantage to plants growing in hot, dry environments, including the ancestors of our most productive crops. Two traits were essential for the evolution of this pathway: increased vein density and the functionalization of bundle sheath cells for photosynthesis. Although GRAS transcriptional regulators, including SHORT ROOT (SHR), have been implicated in mediating leaf patterning in both C3 and C4 species, little is known about what controls the specialized features of the cells that mediate C4 metabolism and physiology. We show in the model monocot, Setaria viridis, that SHR regulates components of multiple cell identities, including chloroplast biogenesis and photosynthetic gene expression in bundle sheath cells, a central feature of C4 plants. Furthermore, we found that it also contributes to the two-cell compartmentalization of the characteristic four-carbon shuttle pathway. Disruption of SHR function clearly reduced photosynthetic capacity and seed yield in mutant plants under heat stress. Together, these results show how cell identities are remodeled by SHR to host the suite of traits characteristic of C4 regulation, which are a main engineering target in non-C4 crops to improve climate resilience.

plant biology↗