UC Davis

This study explores the genetic complexities and evolutionary dynamics of plantadaptation across species within the Brassicaceae family, focusing on Brassica napus, Streptanthus diversifolius, and exploring gene expression related to seed germination and climate adaptation in the Streptanthoid complex. For Brassica napus, an important oilseed crop and an allotetraploid hybrid of Brassica rapa and Brassica oleracea, we utilized third generation sequencing and assembly technologies to generate a new high quality genome assembly of the synthetic cultivar Da-Ae. This work identifies homoeologous exchange hotspots, illuminating the genetic rearrangements essential for hybrid viability. In parallel, we present a chromosome- level genome assembly for Streptanthus diversifolius, also utilizing third generation sequencing technologies. This assembly sheds light on the species' ability to adapt to diverse Californian environments, potentially facilitated by a tribe-specific whole genome duplication event, enhancing its capacity to thrive in inhospitable conditions like serpentine soils. Further, through germination assays and RNA sequencing across multiple California Jewelflower species, we construct gene co-expression networks to correlate with germination and climate adaptation traits. Our findings reveal distinct gene expression patterns driven by climate variations and posit that positive selection has shaped these networks, optimizing germination timing for adaptive success. Collectively, these studies enhance our understanding of the genetic underpinnings of plant adaptability and evolution, showcasing the intricate relationship between genomic architecture, environmental adaptation, and evolutionary innovation in the Brassicaceae family.