The YABBY family of plant-specific transcription factors play important regulatory roles during the development of leaves and floral organs, but their functions in Brassica species are incompletely understood. Here, we identified 79 YABBY genes from Arabidopsis thaliana and five Brassica species (B. rapa, B. nigra, B. oleracea, B. juncea, and B. napus). A phylogenetic analysis of YABBY proteins separated them into five clusters (YAB1–YAB5) with representatives from all five Brassica species, suggesting a high degree of conservation and similar functions within each subfamily. We determined the gene structure, chromosomal location, and expression patterns of the 21 BnaYAB genes identified, revealing extensive duplication events and gene loss following polyploidization. Changes in exon–intron structure during evolution may have driven differentiation in expression patterns and functions, combined with purifying selection, as evidenced by Ka/Ks values below 1. Based on transcriptome sequencing data, we selected nine genes with high expression at the flowering stage. qRT-PCR analysis further indicated that most BnaYAB family members are tissue-specific and exhibit different expression patterns in various tissues and organs of B. napus. This preliminary study of the characteristics of the YABBY gene family in the Brassica napus genome provides theoretical support and reference for the later functional identification of the family genes.

Phosphorus transporter (PHT) genes encode H2PO4−/H+ co-transporters that absorb and transport inorganic nutrient elements required for plant development and growth and protect plants from heavy metal stress. However, little is known about the roles of PHTs in Brassica compared to Arabidopsis thaliana. In this study, we identified and extensively analyzed 336 PHTs from three diploid (B. rapa, B. oleracea, and B. nigra) and two allotetraploid (B. juncea and B. napus) Brassica species. We categorized the PHTs into five phylogenetic clusters (PHT1–PHT5), including 201 PHT1 homologs, 15 PHT2 homologs, 40 PHT3 homologs, 54 PHT4 homologs, and 26 PHT5 homologs, which are unevenly distributed on the corresponding chromosomes of the five Brassica species. All PHT family genes from Brassica are more closely related to Arabidopsis PHTs in the same vs. other clusters, suggesting they are highly conserved and have similar functions. Duplication and synteny analysis revealed that segmental and tandem duplications led to the expansion of the PHT gene family during the process of polyploidization and that members of this family have undergone purifying selection during evolution based on Ka/Ks values. Finally, we explored the expression profiles of BnaPHT family genes in specific tissues, at various developmental stages, and under heavy metal stress via RNA-seq analysis and qRT-PCR. BnaPHTs that were induced by heavy metal treatment might mediate the response of rapeseed to this important stress. This study represents the first genome-wide analysis of PHT family genes in Brassica species. Our findings improve our understanding of PHT family genes and provide a basis for further studies of BnaPHTs in plant tolerance to heavy metal stress.

The authors describe an efficient algorithm design for lossless video compression by using MPEG-2 as a basic research platform. Starting from MPEG motion estimation and compensation, the proposed algorithm focuses on a context tree design to fine tune the statistics and thus optimise the estimation of conditional probabilities to drive an arithmetic coder. In comparison with the existing work on context tree design, the proposed algorithm features: (i) prefix sequence matching to locate the statistics model at the internal node nearest to the stopping point, where successful match of context sequence is broken; (ii) traversing the context tree along a fixed order of context structure with a maximum number of four motion compensated errors; and (iii) context thresholding to quantise the higher end of error values into a single statistics cluster. As a result, the proposed algorithm is able to achieve competitive processing speed, low computational complexity and high compression performances, which bridges the gap between universal statistics modelling and practical compression techniques. When JPEG-LS and CALIC, the existing state-of-the-art in lossless compression of still images, are applied to those motion compensated error-frames as well as individual non-predicted frames to formulate benchmarks, the authors' experiments illustrate that the proposed algorithm outperforms JPEG-LS by up to 24% and CALIC by up to 22%, yet the processing time ranges from less than 2 s per frame to 6 s per frame on a typical PC computing platform

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