M. Lv

The Tarenaya hassleriana Genome Provides Insight into Reproductive Trait and Genome Evolution of Crucifers

A comparative analysis of the genome of the spider flower (Tarenaya hassleriana) from the Brassicaceae sister family, the Cleomaceae, with Arabidopsis and Brassica crops shows that genome evolution following ancient polyploidy and gene duplication events affect reproductively important traits, including floral development and self-incompatibility systems. The Brassicaceae, including Arabidopsis thaliana and Brassica crops, is unmatched among plants in its wealth of genomic and functional molecular data and has long served as a model for understanding gene, genome, and trait evolution. However, genome information from a phylogenetic outgroup that is essential for inferring directionality of evolutionary change has been lacking. We therefore sequenced the genome of the spider flower (Tarenaya hassleriana) from the Brassicaceae sister family, the Cleomaceae. By comparative analysis of the two lineages, we show that genome evolution following ancient polyploidy and gene duplication events affect reproductively important traits. We found an ancient genome triplication in Tarenaya (Th-α) that is independent of the Brassicaceae-specific duplication (At-α) and nested Brassica (Br-α) triplication. To showcase the potential of sister lineage genome analysis, we investigated the state of floral developmental genes and show Brassica retains twice as many floral MADS (for MINICHROMOSOME MAINTENANCE1, AGAMOUS, DEFICIENS and SERUM RESPONSE FACTOR) genes as Tarenaya that likely contribute to morphological diversity in Brassica. We also performed synteny analysis of gene families that confer self-incompatibility in Brassicaceae and found that the critical SERINE RECEPTOR KINASE receptor gene is derived from a lineage-specific tandem duplication. The T. hassleriana genome will facilitate future research toward elucidating the evolutionary history of Brassicaceae genomes.

Nuclear modification factor in intermediate-energy heavy-ion collisions

The transverse momentum dependent nuclear modification factor (NMF), namely R-CP, is investigated for protons produced in Au + Au at 1A GeV within the framework of the isospin-dependent quantum molecular dynamics (IQMD) model. It is found that the radial collective motion during the expansion stage affects the NMF at low transverse momentum a lot. By fitting the transverse mass spectra of protons with the distribution function from the Blast-Wave model, the magnitude of radial flow can be extracted. After removing the contribution from radial flow, the R-CP can be regarded as a thermal one and is found to keep unitary at transverse momentum lower than 0.6 GeV/c and enhance at higher transverse momentum, which can be attributed to the Cronin effect