Multispecies polyploidization, chromosome shuffling, and genome extraction in Zea/Tripsacum hybrids

Area of Science:

• Plant genetics and breeding
• Polyploid evolution
• Genomic stability

Background:

• Polyploidization is a key driver of plant speciation and crop improvement.
• Understanding genome behavior in newly formed polyploids is crucial for their domestication and utilization.
• Maize (Zea mays), perennial teosinte (Zea perennis), and gama grass (Tripsacum dactyloides) offer diverse genetic resources.

Purpose of the Study:

• To construct amphitetraploid maize using nascent allotetraploids as a genetic bridge.
• To investigate transgenerational chromosome inheritance, subgenome stability, and chromosome rearrangements.
• To analyze the impact of these genomic changes on organism fitness and explore mechanisms of polyploid species formation.

Main Methods:

• Hybridization and specialized sexual reproduction to create allohexaploid and subsequent polyploid lines.
• Fertility phenotyping to assess reproductive success and viability.
• Molecular cytogenetic techniques, including genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH), for chromosome analysis.

Main Results:

• Successful construction of amphitetraploid maize via self-fertile allotetraploids derived from maize, Z. perennis, and T. dactyloides.
• Progenies exhibited high variability in chromosome numbers (2n = 35-84) and subgenomic proportions.
• Near-allotetraploid progenies (2n ≈ 40) showed persistent genomic changes but stabilized chromosome numbers and rDNA integrity over six selfed generations, with decreasing variations.

Conclusions:

• Diversified sexual reproduction and genome elimination can lead to novel, self-fertile polyploids.
• Nascent polyploids undergo dynamic genomic changes but can achieve relative stability, providing insights into karyotype evolution.
• The study elucidates mechanisms for genome stability and evolution in polyploid species formation, with implications for crop breeding.