AUTHOR=Reddy Vaishnavi Amarr , Saju Jolly Madathiparambil , Nadimuthu Kumar , Sarojam Rajani 

TITLE=A non-canonical Aux/IAA gene MsIAA32 regulates peltate glandular trichome development in spearmint

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1284125

DOI=10.3389/fpls.2024.1284125

ISSN=1664-462X

ABSTRACT=<p>Phytohormone auxin controls various aspects of plant growth and development. The typical auxin signalling involves the degradation of canonical Aux/IAA proteins upon auxin perception releasing the auxin response factors (ARF) to activate auxin-regulated gene expression. Extensive research has been pursued in deciphering the role of canonical Aux/IAAs, however, the function of non-canonical <italic>Aux/IAA</italic> genes remains elusive. Here we identified a non-canonical <italic>Aux/IAA</italic> gene, <italic>MsIAA32</italic> from spearmint (<italic>Mentha spicata</italic>), which lacks the TIR1-binding domain and shows its involvement in the development of peltate glandular trichomes (PGT), which are the sites for production and storage of commercially important essential oils. Using yeast two-hybrid studies, two canonical Aux/IAAs, MsIAA3, MsIAA4 and an ARF, MsARF3 were identified as the preferred binding partners of MsIAA32. Expression of a R2R3-MYB gene <italic>MsMYB36</italic> and a cyclin gene <italic>MsCycB2-4</italic> was altered in <italic>MsIAA32</italic> suppressed plants indicating that these genes are possible downstream targets of MsIAA32 mediated signalling. Ectopic expression of <italic>MsIAA32</italic> in <italic>Arabidopsis</italic> affected non-glandular trichome formation along with other auxin related developmental traits. Our findings establish the role of non-canonical Aux/IAA mediated auxin signalling in PGT development and reveal species-specific functionalization of Aux/IAAs.</p>