Gap-free genome assemblies of two Pyrus bretschneideri cultivars and GWAS analyses identify a CCCH zinc finger protein as a key regulator of stone cell formation in pear fruit

Abstract

The Chinese white pear (Pyrus bretschneideri) is an economically significant fruit crop worldwide. Previous versions of the P. bretschneideri genome assembly contain numerous gaps and unanchored genetic regions. Here, we generated two high-quality, gap-free genome assemblies for 'Dangshansu' (DS; 503.92 Mb) and 'Lianglizaosu' (ZS; 509.01 Mb), each anchored to 17 chromosomes, achieving a benchmarking universal single-copy ortholog completeness score of nearly 99.0%. Our genome-wide association studies explored the associations between genetic variations and stone cell traits, revealing a significant association peak on DS chromosome 3 and identifying a novel non-tandem CCCH-type zinc finger gene, designated PbdsZF. Through genetic transformation, we verified the pivotal role of PbdsZF in regulation of both lignin biosynthesis and stone cell formation, as it transcriptionally activates multiple genes involved in these processes. By binding to the CT-rich motifs CT1 (CTTTTTTCT) and CT2 (CTCTTTTT), PbdsZF significantly influences the transcription of genes essential for lignin production, underscoring its regulatory importance in plant lignin metabolism. Our study illuminates the complex biology of fruit development and delineates the gene regulatory networks that influence stone cell and lignocellulose formation, thereby enriching genetic resources and laying the groundwork for the molecular breeding of perennial trees.