OsLHY is involved in regulating flowering through the Hd1- and Ehd1- mediated pathways in rice (Oryza sativa L.).

Flowering time (or heading date in crops) is a critical agronomic trait for rice reproduction and adaptation. The circadian clock is an endogenous oscillator that is involved in controlling photoperiodic flowering. The rice LATE ELONGATED HYPOCOTYL (OsLHY), the core oscillator component of circadian clock, is a homolog of the LHY/CCA1 in Arabidopsis. Here we showed that CRISPR/Cas9-engineered mutations in OsLHY caused late flowering in rice only under natural long-day (nLD) and short-day (nSD) conditions, but not artificial SD (10 h light/14 h dark) conditions. In the oslhy mutant, the diurnal expression of circadian clock-related genes was seriously affected under both LD and SD conditions. Furthermore, the expression of the flowering activators Ehd1, Hd3a and RFT1 was down-regulated and flowering repressors Hd1 and Ghd7 was up-regulated in the oslhy mutant under LD conditions. While the transcripts of flowering-related genes were not dramatically influenced under SD conditions. Dual-luciferase assays showed that OsLHY repressed the transcription of OsGI, Hd1, Ghd7, Hd3a, RFT1 and OsELF3, and activated the transcription of Ehd1. Moreover, the yeast one hybrid assay and electrophoretic mobility shift assay confirmed that OsLHY directly repressed OsGI, RFT1 and OsELF3 by binding to their promoters, which is consistent with that in Arabidopsis. These results suggested that the OsLHY can promote rice flowering mainly through regulating Hd1 and Ehd1.

Natural variation and evolutionary dynamics of transposable elements in Brassica oleracea based on next-generation sequencing data.

Brassica oleracea comprises various economically important vegetables and presents extremely diverse morphological variations. They provide a rich source of nutrition for human health and have been used as a model system for studying polyploidization. Transposable elements (TEs) account for nearly 40% of the B. oleracea genome and contribute greatly to genetic diversity and genome evolution. Although the proliferation of TEs has led to a large expansion of the B. oleracea genome, little is known about the population dynamics and evolutionary activity of TEs. A comprehensive mobilome profile of 45,737 TE loci was obtained from resequencing data from 121 diverse accessions across nine B. oleracea morphotypes. Approximately 70% (32,195) of the loci showed insertion polymorphisms between or within morphotypes. In particular, up to 1221 loci were differentially fixed among morphotypes. Further analysis revealed that the distribution of the population frequency of TE loci was highly variable across different TE superfamilies and families, implying a diverse expansion history during host genome evolution. These findings provide better insight into the evolutionary dynamics and genetic diversity of B. oleracea genomes and will potentially serve as a valuable resource for molecular markers and association studies between TE-based genomic variations and morphotype-specific phenotypic differentiation.

Transcriptome analysis of the thermosensitive genic male-sterile line provides new insights into fertility alteration in rice (Oryza sativa).

Thermosensitive genic male-sterile (TGMS) lines have been widely used for rice breeding to produce hybrid rice. Here, RNA-Seq was performed to investigate the expression profiles of young panicle from rice TGMS line at the microspore mother cell and meiosis stages under sterile and fertile conditions. A total of 1070 differentially expressed genes (DEGs) were identified, which were enriched in protein folding, protein binding, regulation of transcription, transcription factor activity and metabolic related processes. Further analyses showed hub genes UbL40s were predicted to interact with proteolysis-related genes and DNA-directed RNA polymerase subunit, and HSPs interacted with kinases to play important roles in regulating fertility alteration. It suggested that besides UbL40s, DNA-directed RNA polymerase subunit, kinases and HSPs might be involved in fertility alteration in rice TGMS lines. These findings provided new insights into fertility alteration in rice TGMS line, which will benefit for further application of TGMS in rice breeding.