Tris(methylthio)methane Produced by Mortierella hyalina Affects Sulfur
Homeostasis in Arabidopsis
Abstract
Microbial volatiles are important factors in symbiotic interactions with
plants. Mortierella hyalina is a beneficial root-colonizing fungus with
a garlic-like smell, and promotes growth of Arabidopsis seedlings. GC-MS
analysis of the M. hyalina headspace and NMR analysis of the extracted
essential oil identified the sulfur-containing volatile
tris(methylthio)methane (TMTM) as the major compound. Its incorporation
in seedlings was shown by 34S labeling experiment. Under sulfur
deficiency, TMTM downregulated sulfur deficiency-responsive genes,
prevented glucosinolate (GSL) and glutathione (GSH) diminishment, and
sustained plant growth. However, excess TMTM led to accumulation of GSH
and GSL and reduced plant growth. Since TMTM is not directly
incorporated into cysteine, we propose that the volatile from M. hyalina
influences the plant sulfur metabolism by interfering with the GSH
metabolism, and alleviates sulfur imbalances under sulfur stress.