Genomic analyses provide insights into sex differentiation of tetraploid strawberry (Fragaria moupinensis).

The strawberry genus, Fragaria, exhibits a wide range of sexual systems and natural ploidy variation. Nearly, all polyploid strawberry species exhibit separate sexes (dioecy). Research has identified the sex-determining sequences as roughly conserved but with repeatedly changed genomic locations across octoploid strawberries. However, it remains unclear whether tetraploid wild strawberries evolved dioecy independently or shared a common origin with octoploid strawberries. In this study, we investigated the sex determinants of F. moupinensis, a dioecious plant with heterogametic females (ZW). Utilizing a combination of haplotype-resolved genome sequencing of the female F. moupinensis, k-mer-based and coverage-based genome-wide association studies (GWAS), and transcriptomic analysis, we discovered a non-recombining, approximately 33.6 kb W-specific region on chromosome 2a. Within this region, only one candidate sex-determining gene (FmoAFT) was identified. Furthermore, an extensive resequencing of the entire Fragaria genus indicated that the W-specific region displays conservative female specificity across all tetraploid species. This observation suggests that dioecy evolved independently in tetraploid and octoploid strawberries. Moreover, employing virus-induced gene silencing (VIGS), we knocked down the expression of the FmoAFT homologue transcript in cultivated strawberries, revealing its potential role in promoting female functions during early carpel development. We also applied DNA affinity purification sequencing (DAP-seq) and yeast one-hybrid assays to identify potential direct targets of FmoAFT. These insights shed new light on the genetic basis and evolutionary history of sex determination in strawberries, thereby facilitating the formulation of strategies to manipulate sex determination in breeding programs.

Phosphate substances transformation and vivianite formation in P-Fe containing sludge during the transition process of aerobic and anaerobic conditions.

Excess sludge was considered as a promising raw material for phosphorus recovery. In this study, the P-Fe containing sludge came from the aerobic membrane bioreactor with electrocoagulation (EC), which was refluxed to the anaerobic unit for iron reduction. Under anaerobic condition, the ORP and pH maintained at -350 mV and 7.5, which exactly met the conditions for vivianite formation. According to the analysis of X-ray polycrystalline diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), the final product of the sludge after anaerobic condition was mainly vivianite. Microbial analysis showed that there were iron reducing bacteria (IRB) in sludge before and after anaerobic process, including Dechloromonas, Desulfovibrio. Aeromonas and Methanobacterium. During the transition process of aerobic and anaerobic conditions, amorphous phosphate substances in P-Fe containing sludge could be transformed vivianite just with long term standing, which could promote the recovery of phosphate resource from wastewater.