Greater leaf photosynthesis in the field by increasing mesophyll conductance via modified cell wall porosity and thickness in tobacco

Abstract

Mesophyll conductance (gm) describes the ease with which CO2 passes from the sub-stomatal cavities of the leaf to the primary carboxylase of photosynthesis, Rubisco. Increasing gm has been suggested as a means to engineer increases in photosynthesis by increasing [CO2] at Rubisco, inhibiting oxygenation and accelerating carboxylation. Here tobacco was transgenically up-regulated with Arabidopsis Cotton Golgi-related 3 (CGR3), a gene controlling methylesterification of pectin, as a strategy to increase CO2 diffusion across the cell wall and thereby increase gm. Across three independent events in tobacco strongly expressing AtCGR3, mesophyll cell wall thickness was decreased by 7-13%, wall porosity increased by 75%, and gm measured by carbon isotope discrimination increased by 28%. Importantly, field-grown plants showed an average 8% increase in leaf photosynthetic CO2 uptake. Upregulating CGR3 provides a new strategy for increasing gm in dicotyledonous crops, leading to higher CO2 assimilation and a potential means to sustainable crop yield improvement.

Adapting C4photosynthesis to atmospheric change and increasing productivity by elevating Rubisco content in Sorghum and Sugarcane

“…Total protein was extracted from 1.9 cm 2 of leaf tissue from the youngest fully expanded leaf of greenhouse-grown sorghum and sugarcane and field-grown sorghum. Protein extraction and western blots were performed as described previously 50 . The following primary antibodies were used: anti-HA (AS12 2220, Agrisera) at a 1:5000 dilution, anti-LS (AS03 037, Agrisera) at a 1:10000 dilution, anti-FLAG (F7425-.2MG, Sigma-Aldrich) at a 1:5000 dilution and anti-RAF1 (custom rabbit antibody, Pacific Immunology) at a 1:1000 dilution.…”

“…Prior to RNA and protein extraction tissue was disrupted and homogenized as described previously 50 . RNA was extracted from 1.9 cm 2 of leaf tissue from the youngest fully expanded leaf of greenhouse and field-grown sorghum, using the NucleoSpin RNA Plant Kit (Macherey-Nagel).…”