Figure 4.

Evolution of AtPDE-Like Proteins and Effect of UVA on Growth and WUE

(A) Cartoon species tree of the major groups of life highlighting the origin and later secondary loss of AtPDE-like proteins. Based on the widespread presence of AtPDE-like proteins in bacteria, archaea, and eukaryotes, we predict an origin of AtPDE-like proteins prior to the last eukaryotic common ancestor highlighted with blue box. AtPDE-like proteins were then conserved in the major groups of eukaryotes before being secondarily lost in the animal stem lineage prior to the diversification of the modern animal groups.

(B and C) Long-term UVA exposure enhances growth and does not affect water-use efficiency. Arabidopsis plants were grown under light tubes supplemented with a combination of blue (λmax = 470 nm) and red (λmax = 660 nm) light coupled or not to UVA light (λmax = 370 nm) (as in Figure 1). All conditions other than presence or absence of UVA were identical (PAR = 120μmol m⁻² s⁻¹, temperature 22/20°C [day/night], relative humidity 70%, 12 h photoperiod). Final plant dry weight was measured at bolting (B). Individual pots were sealed to stop water evaporation from the soil, and each pot was weighed daily from germination until bolting to compute cumulated plant water loss through transpiration. Whole plant water-use efficiency (WUE) was calculated as the ratio between final dry weight and cumulated water loss (C). Data represent means (+/− SE) of 8 plants per genotype and light scenario. Statistical analyses were performed by one-way ANOVA with Tukey post hoc analysis, and letters show significant differences at p < 0.05.

See also Figure S2 and Data S1 for more information. See also Figure S4.