Previous studies suggested thatHd1promoted heading under short-day conditions (SD) and delayed heading under long-day conditions (LD). However in this study,Hd1was demonstrated to consistently promote heading date in Zhenshan 97 (ZS97) background by upregulatingEhd1,Hd3aandRFT1expression under both SD and LD. While the high photoperiod sensitivity ofHd1was observed in Minghui 63 (MH63) background, with heading being suppressed in LD but promoted in SD. Comparative analysis of two sets of near isogenic lines ofHd1in MH63 and ZS97 backgrounds indicated that the alternative functions ofHd1in promoting or suppressing heading under LD are dependent on the previously cloned flowering repressor geneGhd7. The interaction between proteins Ghd7 and Hd1 occurred through binding of the CCT domain of Ghd7 to the transcription-activating domain of Hd1, resulting in suppression ofEhd1and florigen gene expression. The involvement of the transcription-activating domain of Hd1 in this protein-protein interaction probably blocked or weakened its transcriptional activity. These findings suggest thatHd1alone essentially acts as a promoter of heading date, and the protein interaction between Ghd7 and Hd1 determines photoperiod sensitivity and integratedHd1-mediated andEhd1-mediated flowering pathways in rice.

Summary: The size of cultivated rice (Oryza sativa) grains has been altered by both domestication and artificial selection over the course of evolutionary history. Several quantitative trait loci (QTLs) for grain size have been cloned in the past 10 yr. To explore the natural variation in these QTLs, resequencing of grain width and weight 2 (GW2), grain size 5 (GS5) and QTL for seed width 5 (qSW5) and genotyping of grain size 3 (GS3) were performed in the germplasms of 127 varieties of rice (O. sativa) and 10–15 samples of wild rice (Oryza rufipogon). Ten, 10 and 15 haplotypes were observed for GW2, GS5 and qSW5. qSW5 and GS3 had the strongest effects on grain size, which have been widely utilized in rice production, whereas GW2 and GS5 showed more modest effects. GS5 showed small sequence variations in O. sativa germplasm and that of its progenitor O. rufipogon. qSW5 exhibited the highest level of nucleotide diversity. GW2 showed signs of purifying selection. The four grain size genes experienced different selection intensities depending on their genetic effects. In the indica population, linkage disequilibrium (LD) was detected among GS3, qSW5 and GS5. The substantial genetic variation in these four genes provides the flexibility needed to design various rice grain shapes. These findings provide insight into the evolutionary features of grain size genes in rice.

In China, saline–alkali lands constitute 5.01% of the total land area, having a significant impact on both domestic and international food production. Rapeseed (Brassica napus L.), as one of the most important oilseed crops in China, has garnered considerable attention due to its potential adaptability to saline conditions. Breeding and improving salt-tolerant varieties is a key strategy for the effective utilization of saline lands. Hence, it is important to conduct comprehensive research into the adaptability and salt tolerance mechanisms of Brassica napus in saline environments as well as to breed novel salt-tolerant varieties. This review summarizes the molecular mechanism of salt tolerance, physiological and phenotypic indexes, research strategies for the screening of salt-tolerant germplasm resources, and genetic engineering tools for salt stress in Brassica napus. It also introduces various agronomic strategies for applying exogenous substances to alleviate salt stress and provide technological tools and research directions for future research on salt tolerance in Brassica napus.