Greater Aperture Counteracts Effects of Reduced Stomatal Density on WUE: A Case Study on Sugarcane and Meta-Analysis

Themes: Feedstock Production

Keywords: Phenotyping, Water Use Efficiency

Citation

Lunn, D., Kannan, B., Germon, A., Leverett, A., Clemente, T.E., Altpeter, F., Leakey, A.D.B. July 12, 2024. Dataset for “Greater Aperture Counteracts Effects of Reduced Stomatal Density on WUE: A Case Study on Sugarcane and Meta-Analysis.” University of Illinois Urbana-Champaign. DOI: 10.13012/B2IDB-9701546_V1.

Overview

Stomatal regions with more than one stomatal-containing file in wildtype (WT) transgenic sugarcane over-expressing SbEPF2 (SbEPF2-15). Panels show (A) adaxial and (B) abaxial stomatal regions with more than one stomatal-containing file. Graphs show box plots of the 25th and 75th percentile with a line indicating the median value. Each box plot shows the mean with a white circle and grey dots showing individual observed residual data points (n=10) where letters within each panel indicate significant differences between genotypes.

Stomata regulate CO₂ and water vapor exchange between leaves and the atmosphere. Stomata are a target for engineering to improve crop intrinsic water use efficiency (iWUE). One example is by expressing genes that lower stomatal density (SD) and reduce stomatal conductance (g_sw). However, the quantitative relationship between reduced SD, g_sw, and the mechanisms underlying it is poorly understood. We addressed this knowledge gap using low-SD sugarcane (Saccharum spp. hybrid) as a case study alongside a meta-analysis of data from 10 species. Transgenic expression of EPIDERMAL PATTERNING FACTOR 2 from Sorghum bicolor (SbEFP2) in sugarcane reduced SD by 26-38% but did not affect g_sw compared to wildtype. Further, no changes occurred in stomatal complex size or proxies for photosynthetic capacity. Measurements of gas exchange at low CO₂ concentrations that promote complete stomatal opening to normalize aperture size between genotypes were combined with modeling of maximum g_sw from anatomical data. These data suggest that increased stomatal aperture is the only possible explanation for maintaining g_sw when SD is reduced. Meta-analysis across C₃ dicots, C₃ monocots, and C₄ monocots revealed engineered reductions in SD are strongly correlated with lower g_sw (r2=0.60-0.98), but this response is damped relative to the change in anatomy.

Data

Illinois Data Bank – stomatal patterning, expression data, and leaf physiology

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