Evidence for wheat-rye nucleolar competition (amphiplasty) in triticale by silver-staining procedure

Area of Science:

• Plant genetics
• Cytogenetics
• Molecular biology

Background:

• Hexaploid triticale is an artificial amphiploid of tetraploid wheat and diploid rye.
• Amphiplasty, the phenomenon of gene expression modification in hybrids, is crucial for understanding interspecific gene interactions.
• Nucleolar organizer regions (NORs) are key sites for ribosomal DNA (rDNA) gene activity.

Purpose of the Study:

• To analyze amphiplasty in hexaploid triticale using a modified silver-staining technique.
• To compare the nucleolar organizer regions (Ag-NORs) of triticale with its parental species: durum wheat and rye.
• To assess the functionality of rDNA sites and gene expression in the hybrid.

Main Methods:

• A modified, highly reproducible silver-staining procedure was employed.
• Comparative analysis of metaphase somatic cells using phase contrast, C-banding, and silver-staining.
• Identification and characterization of Ag-NORs in hexaploid triticale cv. 'Cachirulo', tetraploid durum wheat cv. 'Enano de Andujar', and diploid rye cv. 'Petkus'.

Main Results:

• Two Ag-NORs (chromosome pair 1R) were observed in all analyzed rye plants.
• Four Ag-NORs (chromosome pairs 1B and 6B) were found in both the tetraploid wheat parent and the triticale.
• The rye Ag-NORs were absent in the hexaploid triticale, suggesting suppression of rye rDNA gene activity.

Conclusions:

• The modified silver-staining method effectively visualizes gene functionality at rDNA sites.
• Amphiplasty in triticale leads to the suppression of rye NORs, indicating differential gene expression.
• This technique is valuable for studying amphiplasty in hybrid combinations within the Triticum group and related species.