The photoperiodic response is one of the most important factors determining heading date in rice (Oryza sativa). Although rhythmic expression patterns of flowering time genes have been reported to fine-tune the photoperiodic response, posttranslational regulation of key flowering regulators has seldom been elucidated in rice. Heading date 1 (Hd1) encodes a zinc finger transcription factor that plays a crucial role in the photoperiodic response, which determines rice regional adaptability. However, little is known about the molecular mechanisms of Hd1 accumulation during the photoperiod response. Here, we identify a C3HC4 RING domain-containing E3 ubiquitin ligase, Heading date Associated Factor 1 (HAF1), which physically interacts with Hd1. HAF1 mediates ubiquitination and targets Hd1 for degradation via the 26S proteasomedependent pathway. The haf1 mutant exhibits a later flowering heading date under both short-day and long-day conditions. In addition, the haf1 hd1 double mutant headed as late as hd1 plants under short-day conditions but exhibited a heading date similar to haf1 under long-day conditions, thus indicating that HAF1 may determine heading date mainly through Hd1 under short-day conditions. Moreover, high levels of Hd1 accumulate in haf1. Our results suggest that HAF1 is essential to precise modulation of the timing of Hd1 accumulation during the photoperiod response in rice.

A low seed glucosinolate resource was developed in polyploid B. napus using a method that identifies the functions of genes with rare or no genetic variation.

Cupin_1 domain-containing proteins (CDPs) are ubiquitously present in higher plants, which are known to play essential roles in various biological processes. In this study, we carried out genome-wide characterization and systematic investigation of the CDP genes in Brassica napus. A total of 96 BnCDPs, including 71 germin-like proteins (GLPs; proteins with a single cupin_1 domain) and 25 CDP bicupins (proteins with two cupin_1 domains), were identified and clustered into six distinct subfamilies (I–VI) based on the phylogenic analysis, gene structure and motif distribution. Further analysis indicated that whole-genome duplication (WGD) and segmental duplication are main contributors to the species-specific expansion of the BnCDP gene family, and all the duplicated genes subsequently underwent strong purification selection. The promoter region of BnCDPs showed enrichment of cis-regulatory elements associated with development, hormone and stress, as well as transcription factor binding sites, which validates the prediction that BnCDPs are widely involved in plant growth and biotic and abiotic stress responses. The BnCDPs in different subfamilies exhibited obvious differences in expression among 30 developmental tissues/stages of B. napus, implying that BnCDPs may be involved in tissue- and stage-specific developmental processes. Similar trends in expression of most BnCDPs were observed under Sclerotinia sclerotiorum inoculation and four abiotic stresses (dehydration, cold, ABA and salinity), particularly the BnGLPs in subfamily I and III with single cupin_1 domain, revealing that BnCDPs are of great importance in the environmental adaption of B. napus. We then performed a genome-wide association study (GWAS) of 274 B. napus core germplasms on S. sclerotiorum resistance and identified four significantly associated loci harboring five BnGLPs. The expression levels of two candidate genes, BnGLP1.A08 and BnGLP1.C08, were significantly correlated with S. sclerotiorum resistance. Their functional responses to multiple stages of S. sclerotiorum inoculation and four abiotic stresses were further examined through qPCR. Overall, this study provides rich resources for research on the function and evolutionary playground of CDP genes.