The chemical compound bubblin induces stomatal mispatterning in Arabidopsis by disrupting the intrinsic polarity of stomatal lineage cells

Abstract

Stem cell polarization is a crucial step in asymmetric cell division, which is a universal system for generating cellular diversity in multicellular organisms. Several conventional genetics studies have attempted to elucidate the mechanisms underlying cell polarization in plants, but it remains largely unknown. In plants, stomata, which are valves for gas exchange, are generated through several rounds of asymmetric divisions. In this study, we identified and characterized a chemical compound that affects stomatal stem cell polarity. Highthroughput screening for bioactive molecules identified a pyridinethiazole derivative, named bubblin, which induced stomatal clustering in Arabidopsis epidermis. Bubblin perturbed stomatal asymmetric division, resulting in the generation of two identical daughter cells. Both cells continued to express the stomatal fate determinant SPEECHLESS, and then differentiated into mispatterned stomata. Bubblin-treated cells had a defect in the polarized localization of BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL), which is required for asymmetric cell fate determination. Our results suggest that bubblin induces stomatal lineage cells to divide without BASL-dependent pre-mitotic establishment of polarity. Bubblin is a potentially valuable tool for investigating cell polarity establishment in stomatal asymmetric division.

Stomatal Development and Perspectives toward Agricultural Improvement

“…Thus far, four small compounds, Bikinin, Bubblin, CL1, and CL2, have been reported to modulate stomatal development (Kim et al 2012;Sakai et al 2017;Ziadi et al 2017). Bikinin was identified from a commercially available DI-VERSet compound library (ChemBridge) (De Rybel et al 2009).…”

“…Indeed, treatment of Bikinin reduces the number of stomata in a leaf epidermis (Kim et al 2012). Bubblin is a small compound found from a screening of the Library of Active Compounds on Arabidopsis (Zhao et al 2007;Sakai et al 2017). This compound affects asymmetric cell division of MMCs presumably by alternating the correct localization of cell polarity factors including BASL, and, consequently, induces clustered stomata formation in Arabidopsis (Sakai et al 2017).…”

Plant Chemical Genetics: From Phenotype-Based Screens to Synthetic Biology

“…By contrast, natural product libraries and libraries focused on a given phenotype or biological process of interest are smaller and often selected for bioactivity in a given system. For instance, the LATCA collection consists of 3,600 active small molecules able to inhibit hypocotyl growth in etiolated Arabidopsis (Arabidopsis thaliana) seedlings (Yoneda et al, 2007;Zhao et al, 2007;Schreiber et al, 2008;Park et al, 2009;Abdel-Hamid et al, 2011;Forde et al, 2013;Carland et al, 2016;Okubo-Kurihara et al, 2016;Sakai et al, 2017). For such focused collections, small molecules can originate from a number of different, larger libraries.…”

“…Examples of the latter are the discoveries of the compounds hyperphyllin and bubblin (Poretska et al, 2016;Sakai et al, 2017). Application of hyperphyllin mimicked the phenotype of the altered meristem program1 (amp1) mutant, whereas bubblin simulated stomatal clustering mutants.…”

“…The most potent of these RG compounds, soporidine, acted as an antagonist of SL signaling and SL-mediated Striga hermonthica germination. In summary, chemical genetics has Sakai et al, (2017) contributed to the identification of numerous small molecules affecting most of the hormone signaling pathways in plants through phenotype-based screens designed to either suppress or promote selected phenotypes. In all cases, increasing the screening specificity through the use of specialized reporters has yielded compounds with preferential MoAs.…”