Catastrophic Unbalanced Genome Rearrangements Cause Somatic Loss of Berry Color in Grapevine.

Area of Science:

• Plant genetics
• Genomics
• Molecular biology

Background:

• Somatic variants in grapevine (Vitis vinifera) offer pathways to new cultivars.
• The origins of structural variations, such as deletions, remain unclear.

Purpose of the Study:

• To investigate the mutational mechanisms behind somatic structural variation in grapevine.
• To characterize the genomic alterations in the white berry variant Tempranillo Blanco (TB) compared to its black berry ancestor.

Main Methods:

• Whole-genome sequencing of TB and Tempranillo Tinto.
• Analysis of gene deletions, copy number variations, and chromosomal breakpoints.
• Segregation analysis to assess chromosome transmission.

Main Results:

• TB exhibits a catastrophic genome rearrangement with hemizygous deletion of 313 genes, including MYB transcription factors crucial for anthocyanin production.
• Chromothripsis-like patterns, involving multiple intrachromosomal and interchromosomal translocations, were identified.
• Unbalanced genome rearrangements led to reduced gamete viability, compromising fruit set and yield in TB.

Conclusions:

• Catastrophic genome rearrangements, resembling chromothripsis, can occur spontaneously during plant somatic growth.
• These rearrangements generate novel phenotypes, such as altered berry color, which can be valuable for crop improvement in vegetatively propagated species.
• The study elucidates mechanisms of structural variation and their phenotypic consequences in Vitis vinifera.