AUTHOR=Adhikari Prakash Babu , Zhu Shaowei , Liu Xiaoyan , Huang Chen , Xie Liyang , Wu Xiaoyan , He Jiale , Mitsuda Nobutaka , Peters Benjamin , Brownfield Lynette , Nagawa Shingo , Kasahara Ryushiro Dora 

TITLE=Discovery of a cis-regulatory element SaeM involved in dynamic regulation of synergid-specific MYB98

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1177058

DOI=10.3389/fpls.2023.1177058

ISSN=1664-462X

ABSTRACT=<p><italic>MYB98</italic> is a key regulator of the genetic network behind pollen tube attraction toward the female gametophyte. <italic>MYB98</italic> is specifically expressed in the synergid cells (SCs), a female gametophyte component cells specialized for pollen tube attraction. However, it had not been clear how exactly <italic>MYB98</italic> achieves this specific expression pattern. In the current study, we have determined that a normal SC-specific expression of <italic>MYB98</italic> is dependent on a 16-bp-long <italic>cis</italic>-regulatory element, CATTTACACATTAAAA, freshly named as the “<bold><italic><underline>S</underline></italic></bold><italic>ynergid-specific</italic><bold><italic><underline>A</underline></italic></bold><italic>ctivation</italic><bold><italic><underline>E</underline></italic></bold><italic>lement of</italic><bold><italic><underline>M</underline></italic></bold><italic>YB98</italic>” (<italic>SaeM</italic>). An 84 bp fragment harboring <italic>SaeM</italic> in the middle was sufficient to drive exclusively SC-specific expression. The element was present in a significantly large proportion of SC-specific gene promoters and in the promoter of <italic>MYB98</italic> homologous genes in the Brassicaceae (<italic>pMYB98</italic>s). Significance of such family-wide <italic>SaeM-like</italic> element conservation in exclusive SC-specific expression was confirmed by the Arabidopsis-like activation feature of <italic>Brassica oleracea–</italic>derived <italic>pMYB98</italic> and absence of such feature of <italic>pMYB98</italic> derived from a non-Brassicaceae member <italic>Prunus persica</italic>. Additionally, the yeast-one-hybrid assay showed that the <italic>SaeM</italic> can be recognized by ANTHOCYANINLESS2 (ANL2) and DAP-seq data further suggested for additional three ANL2 homologs targeting the similar <italic>cis-</italic>element. Overall, our study has concluded that <italic>SaeM</italic> plays a crucial role in driving exclusively SC-specific expression of <italic>MYB98</italic> and strongly suggests for the involvement of ANL2 and its homologs in its dynamic regulation <italic>in planta</italic>. Future study on the transcription factors is expected to shed more light on the mechanism behind the process.</p>