AUTHOR=Delgado Dolores , Sánchez-Bermejo Eduardo , de Marcos Alberto , Martín-Jimenez Cristina , Fenoll Carmen , Alonso-Blanco Carlos , Mena Montaña 

TITLE=A Genetic Dissection of Natural Variation for Stomatal Abundance Traits in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01392

DOI=10.3389/fpls.2019.01392

ISSN=1664-462X

ABSTRACT=<p>Stomatal abundance varies widely across natural populations of <italic>Arabidopsis thaliana</italic>, and presumably affects plant performance because it influences water and CO<sub>2</sub> exchange with the atmosphere and thence photosynthesis and transpiration. In order to determine the genetic basis of this natural variation, we have analyzed a recombinant inbred line (RIL) population derived from the wild accession Ll-0 and the reference strain Landsberg <italic>erecta</italic> (L<italic>er</italic>), which show low and high stomatal abundance, respectively. Quantitative trait locus (QTL) analyses of stomatal index, stomatal density, and pavement cell density measured in the adaxial cotyledon epidermis, identified five loci. Three of the genomic regions affect all traits and were named <italic>MID</italic> (<italic><underline>M</underline>odulator of Cell <underline>I</underline>ndex and <underline>D</underline>ensity</italic>) 1 to 3. <italic>MID2</italic> is a large-effect QTL overlapping with <italic>ERECTA</italic> (<italic>ER</italic>), the <italic>er-1</italic> allele from L<italic>er</italic> increasing all trait values. Additional analyses of natural and induced loss-of-function <italic>er</italic> mutations in different genetic backgrounds revealed that <italic>ER</italic> dysfunctions have differential and opposite effects on the stomatal index in adaxial and abaxial cotyledon epidermis and confirmed that <italic>ER</italic> is the gene underlying <italic>MID2</italic>. Ll-0 alleles at <italic>MID1</italic> and <italic>MID3</italic> displayed moderate and positive effects on the various traits. Furthermore, detailed developmental studies tracking primary and satellite stomatal lineages show that <italic>MID3</italic>-Ll-0 allele promotes the spacing divisions that initiate satellite lineages, while the <italic>ER</italic> allele limits them. Finally, expression analyses suggest that <italic>ER</italic> and <italic>MID3</italic> modulate satellization through partly different regulatory pathways. Our characterization of <italic>MID3</italic> indicates that genetic modulation of satellization contributes to the variation for stomatal abundance in natural populations, and subsequently that this trait might be involved in plant adaptation.</p>