Fungal Diversity and Gibberellin Hormones Associated with Long Whips of Smut-Infected Sugarcanes

Abstract

Sugarcane smut, caused by the fungus Sporisorium scitamineum (Sydow), significantly affects sugarcane crops worldwide. Infected plants develop whip-like structures known as sori. Significant variations in these whip lengths are commonly observed, but the physiological and molecular differences causing these morphological differences remain poorly documented. To address this, we employed conventional microbe isolation, metagenomic, and metabolomic techniques to investigate smut-infected sugarcane stems and whips of varying lengths. Metagenomics analysis revealed a diverse fungal community in the sugarcane whips, with Sporisorium and Fusarium genera notably present (>1%) in long whips. Isolation techniques confirmed these findings. Ultra-performance liquid chromatography analysis (UHPLC-MS/MS) showed high levels of gibberellin hormones (GA3, GA1, GA4, GA8, and GA7) in long whips, with GA4 and GA7 found exclusively in long whips and stems. Among the prominent genera present within long whips, Fusarium was solely positively correlated with these gibberellin (GA) hormones, with the exception of GA8, which was positively correlated with Sporisorium. KEGG enrichment analysis linked these hormones to pathways like diterpenoid biosynthesis and plant hormone signal transduction. These findings suggest that Fusarium may influence GA production leading to whip elongation. Our study reveals fungal dynamics and gibberellin responses in sugarcane smut whips. Future research will explore the related molecular gibberellin synthesis mechanisms.