Distribution, Polymorphism and Function Characteristics of the GST-Encoding Fhb7 in Triticeae

Area of Science:

• Plant genetics
• Molecular biology
• Crop science

Background:

• The Fhb7 gene, encoding glutathione S-transferase (GST), was previously isolated from Thinopyrum elongatum, conferring resistance to Fusarium head blight (FHB).
• Initial findings suggested Thinopyrum acquired Fhb7 via horizontal gene transfer from an Epichloë species.

Purpose of the Study:

• To investigate the distribution and evolutionary origin of Fhb7 homologs within the Triticeae tribe.
• To re-evaluate the role of Fhb7 in conferring FHB resistance based on its broader presence and potential variations.

Main Methods:

• Bioinformatic analysis using blasting searches to identify Fhb7 homologs.
• Sequence comparisons of Fhb7 homologs across different Triticeae genera.
• Analysis of FHB resistance in wheat-Thinopyrum derivatives carrying Fhb7 homologs.

Main Results:

• Fhb7 homologs are widely distributed across multiple Triticeae genera (Thinopyrum, Elymus, Leymus, Roegneria, Pseudoroegneria), not exclusive to Thinopyrum.
• High protein sequence identity (≥94%) among Fhb7 homologs suggests horizontal gene transfer predates Triticeae differentiation.
• Some wheat-Thinopyrum derivatives with Fhb7 homologs exhibited varied FHB resistance, questioning the gene's sole protective role.

Conclusions:

• The horizontal gene transfer of Fhb7 likely occurred much earlier in Triticeae evolution than previously thought.
• The presence of Fhb7 homologs does not guarantee FHB resistance, indicating other factors influence disease response.
• Further research is needed to understand the functional variations of Fhb7 and its contribution to Fusarium head blight resistance.