SHORTINTERNODE/STYLISH proteins are a highly redundant family of transcriptional activators targeting genes that mediate auxin biosynthesis and are involved in the formation and development of early lateral organs in plants. SHI/STYs not only participate in the development of plant lateral organs, but also help plants resist some biological and abiotic stresses (Kuusk et al., 2006, Fang et al., 2023).

Arabidopsis thaliana has 10 members of the SHI/STY family that have a 43-amino acid RING-like zinc finger domain (pfam05142, TIGR01623), and a more unique C-terminal domain, similar in size, the IGGH domain, which is responsible for intrafamily homo/hetero-dimerization that may be necessary for some of the proteins' functions (Kuusk et al., 2006). In Arabidopsis, AtSTY1 interacts with a promoter element ACTCTA(C/A) in several genes related to auxin biosynthesis, YUC4, YUC8, ORCA3, and ORA59. (Eklund et al., 2010).

In maize, 11 SRS genes with 13 transcripts have been identified and characterized (He et al., 2020). RNA-sequencing data analysis showed that the expression patterns of maize SRS genes were quite different from each other, indicating their divergence in function. Coexpression network analysis suggested that GRMZM2G077752 might perceive ABA signal and cause the activation of carbohydrate remobilization during leaf aging (He et al., 2020). One of these maize SRS genes ZmSRS9 (Lrp1) is expressed in early root primordia and meristems and is auxin-inducible (Zhang et al., 2015). The repression of the transcriptional activator lrp1 by direct binding of the Aux/IAA protein ROOTLESS WITH UNDETECTABLE MERISTEM 1 (RUM1) to its promoter, together with specific expression of lrp1 in root meristems, suggests a function in maize root development via the RUM1-dependent auxin signaling pathway (Zhang et al., 2015).

Last updated June 2023 by John Gray

References:

Eklund DM, Ståldal V, Valsecchi I, Cierlik I, Eriksson C, Hiratsu K, Ohme-Takagi M, Sundström JF, Thelander M, Ezcurra I, Sundberg E. The Arabidopsis thaliana STYLISH1 protein acts as a transcriptional activator regulating auxin biosynthesis. Plant Cell. 2010 Feb;22(2):349-63. doi: 10.1105/tpc.108.064816. Epub 2010 Feb 12. PMID: 20154152; PMCID: PMC2845406.

Fang D, Zhang W, Ye Z, Hu F, Cheng X, Cao J. The plant specific SHORT INTERNODES/STYLISH (SHI/STY) proteins: Structure and functions. Plant Physiol Biochem. 2023 Jan;194:685-695. doi: 10.1016/j.plaphy.2022.12.018. Epub 2022 Dec 20. PMID: 36565613.

Kuusk S, Sohlberg JJ, Magnus Eklund D, Sundberg E. Functionally redundant SHI family genes regulate Arabidopsis gynoecium development in a dose-dependent manner. Plant J. 2006 Jul;47(1):99-111. doi: 10.1111/j.1365-313X.2006.02774.x. Epub 2006 Jun 1. PMID: 16740146.

He B, Shi P, Lv Y, Gao Z, Chen G. Gene coexpression network analysis reveals the role of SRS genes in senescence leaf of maize (Zea mays L.). J Genet. 2020;99:3. PMID: 32089522.

Zhang Y, von Behrens I, Zimmermann R, Ludwig Y, Hey S, Hochholdinger F. LATERAL ROOT PRIMORDIA 1 of maize acts as a transcriptional activator in auxin signalling downstream of the Aux/IAA gene rootless with undetectable meristem 1. J Exp Bot. 2015 Jul;66(13):3855-63. doi: 10.1093/jxb/erv187. Epub 2015 Apr 23. PMID: 25911745; PMCID: PMC4473986.