Reduced photosynthesis in Arabidopsis thaliana atpme17.2 and atpae11.1 mutants is associated to altered cell wall composition.

The cell wall is a complex and dynamic structure that determines plants' performance by constant remodeling of its compounds. Although cellulose is its major load-bearing component, pectins are crucial to determine wall characteristics. Changes in pectin physicochemical properties, due to pectin remodeling enzymes (PRE), induce the rearrangement of cell wall compounds, thus, modifying wall architecture. In this work, we tested for the first time how cell wall dynamics affect photosynthetic properties in Arabidopsis thaliana pectin methylesterase atpme17.2 and pectin acetylesterase atpae11.1 mutants in comparison to wild-type Col-0. Our results showed maintained PRE activities comparing mutants with wild-type and no significant differences in cellulose, but cell wall non-cellulosic neutral sugars contents changed. Particularly, the amount of galacturonic acid (GalA) - which represents to some extent the pectin cell wall proportion - was reduced in the two mutants. Additionally, physiological characterization revealed that mutants presented a decreased net CO2 assimilation (AN ) because of reductions in both stomatal (gs ) and mesophyll conductances (gm ). Thus, our results suggest that atpme17.2 and atpae11.1 cell wall modifications due to genetic alterations could play a significant role in determining photosynthesis.