The dual role of the RETINOBLASTOMA-RELATED protein in the DNA damage response is coordinated by the interaction with LXCXE-containing proteins

Genome-wide association study of haploid female fertility (HFF) and haploid male fertility (HMF) in BS39-derived doubled haploid maize lines

KEY MESSAGE

Restoration of haploid female and haploid male fertility without colchicine is feasible. Three SNPs and eight gene models for HFF, and one SNP and a gene model for HMF were identified. Doubled haploid (DH) breeding accelerates the development of elite inbred lines and facilitates the incorporation of exotic germplasm, offering a powerful tool for maize improvement. Traditional DH breeding relies on colchicine to induce haploid genome doubling. Colchicine is toxic, and its application is labor-intensive, with most genotypes recording low genome doubling rates (10-30%). This study investigates spontaneous haploid genome doubling (SHGD) as a safer and more efficient alternative to colchicine. We evaluated the effectiveness of SHGD in restoring haploid female fertility (HFF) and haploid male fertility (HMF) without colchicine. Using genome-wide association studies (GWAS), we identified genomic regions influencing HFF and HMF. The plant materials included the BS39-haploid isogenic lines (HILs) and BS39-SHGD-haploid isogenic lines (HILs). Our results revealed significant SNP associations for both traits, with candidate genes involved in cell cycle regulation, cytoskeletal organization, and hormonal signaling. Analysis of variance (ANOVA) revealed significant variation in HFF across haploids and two environments. Similarly, HMF showed substantial differences across haploids and between the two environments. Spearman correlation between HFF and HMF showed no correlation (r = -0.03) between the two traits. HFF showed high heritability (0.8), indicating strong genetic control, whereas HMF displayed moderate heritability (0.5), suggesting additional environmental influences. The findings underscore the potential of SHGD to enhance DH breeding efficiency and support the development of new maize varieties tailored to diverse agricultural needs.

Mechanistic insights into DNA damage recognition and checkpoint control in plants

The plant DNA damage response (DDR) pathway safeguards genomic integrity by rapid recognition and repair of DNA lesions that, if unrepaired, may cause genome instability. Most frequently, DNA repair goes hand in hand with a transient cell cycle arrest, which allows cells to repair the DNA lesions before engaging in a mitotic event, but consequently also affects plant growth and yield. Through the identification of DDR proteins and cell cycle regulators that react to DNA double-strand breaks or replication defects, it has become clear that these proteins and regulators form highly interconnected networks. These networks operate at both the transcriptional and post-transcriptional levels and include liquid-liquid phase separation and epigenetic mechanisms. Strikingly, whereas the upstream DDR sensors and signalling components are well conserved across eukaryotes, some of the more downstream effectors are diverged in plants, probably to suit unique lifestyle features. Additionally, DDR components display functional diversity across ancient plant species, dicots and monocots. The observed resistance of DDR mutants towards aluminium toxicity, phosphate limitation and seed ageing indicates that gaining knowledge about the plant DDR may offer solutions to combat the effects of climate change and the associated risk for food security.