The effect of loss-of-function of adaxially or abaxially enriched genes on stomatal patterning in Arabidopsis thaliana

Abstract

Stomatal pores regulate CO₂ uptake for photosynthesis and water loss via transpiration. In amphistomatous species such as Arabidopsis thaliana, stomata occur on both lower and upper leaf surfaces, yet the mechanisms that control their distribution between leaf surfaces and potential surface-specific functions remain unclear. Here, I analysed stomatal patterning and conductance in loss-of-function mutants of genes enriched in the stomatal lineage cells and preferentially expressed in specific leaf surfaces. Most mutants did not differ from wild type plants in stomatal density or stomatal ratio. However, stomatal index was increased in el19y-2, prx34, and el21x-1 on the abaxial surface, and in el19y-2 on the adaxial surface too, indicating effects of respective genes on stomatal lineage progression. In a subsequent experiment the scrm mutant showed reduced stomatal density on both leaf surfaces. Despite this, scrm exhibited increased adaxial stomatal conductance and higher conductance per individual stoma on both leaf surfaces, suggesting more open stomata. These results show that the studied genes have limited effects on stomatal distribution, but some of them can influence stomatal development. This work supports partially independent regulation of stomatal traits between leaf surfaces.