Roles of the MYB94/FUSED LEAVES1 (ZmFDL1) and GLOSSY2 (ZmGL2) genes in cuticle biosynthesis and potential impacts on Fusarium verticillioides growth on maize silks

Giulia Castorina; Madison Bigelow; Travis Hattery; Massimo Zilio; Stefano Sangiorgio; Elisabetta Caporali; Giovanni Venturini; Marcello Iriti; Marna D Yandeau-Nelson; Gabriella Consonni

doi:10.3389/fpls.2023.1228394

Roles of the MYB94/FUSED LEAVES1 (ZmFDL1) and GLOSSY2 (ZmGL2) genes in cuticle biosynthesis and potential impacts on Fusarium verticillioides growth on maize silks

Front Plant Sci. 2023 Jul 20:14:1228394. doi: 10.3389/fpls.2023.1228394. eCollection 2023.

Affiliations

¹ Dipartimento Di Scienze Agrarie e Ambientali (DiSAA), Università Degli Studi Di Milano, Milan, Italy.
² Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States.
³ Dipartimento Di Bioscienze, Università Degli Studi Di Milano, Milan, Italy.

Abstract

Maize silks, the stigmatic portions of the female flowers, have an important role in reproductive development. Silks also provide entry points for pathogens into host tissues since fungal hyphae move along the surface of the silks to reach the site of infection, i.e., the developing kernel. The outer extracellular surface of the silk is covered by a protective hydrophobic cuticle, comprised of a complex array of long-chain hydrocarbons and small amounts of very long chain fatty acids and fatty alcohols. This work illustrates that two previously characterized cuticle-related genes separately exert roles on maize silk cuticle deposition and function. ZmMYB94/FUSED LEAVES 1 (ZmFDL1) MYB transcription factor is a key regulator of cuticle deposition in maize seedlings. The ZmGLOSSY2 (ZmGL2) gene, a putative member of the BAHD superfamily of acyltransferases with close sequence similarity to the Arabidopsis AtCER2 gene, is involved in the elongation of the fatty acid chains that serve as precursors of the waxes on young leaves. In silks, lack of ZmFDL1 action generates a decrease in the accumulation of a wide number of compounds, including alkanes and alkenes of 20 carbons or greater and affects the expression of cuticle-related genes. These results suggest that ZmFDL1 retains a regulatory role in silks, which might be exerted across the entire wax biosynthesis pathway. Separately, a comparison between gl2-ref and wild-type silks reveals differences in the abundance of specific cuticular wax constituents, particularly those of longer unsaturated carbon chain lengths. The inferred role of ZmGL2 is to control the chain lengths of unsaturated hydrocarbons. The treatment of maize silks with Fusarium verticillioides conidia suspension results in altered transcript levels of ZmFDL1 and ZmGL2 genes. In addition, an increase in fungal growth was observed on gl2-ref mutant silks 72 hours after Fusarium infection. These findings suggest that the silk cuticle plays an active role in the response to F. verticillioides infection.

Keywords: Fusarium ear rot; Fusarium resistance; Fusarium verticillioides; biotic stress; cuticle; cuticular wax; maize; silk.

Grants and funding

This research was supported by the United State National Science Foundation grant IOS-1546272 to MDY-N, NIFA‐USDA Hatch project IOW03649 (MDY-N) and through Iowa State University’s Center for Metabolic Biology. The content of this paper is however solely the responsibility of the authors and does not represent the official views of the NSF. Open access publication fees were provided to GCa and GCo by the University of Milan through the APC initiative.