Karyotyping of aneuploid and polyploid plants from low coverage whole-genome resequencing.

BACKGROUND: Karyotype, as a basic characteristic of species, provides valuable information for fundamental theoretical research and germplasm resource innovation. However, traditional karyotyping techniques, including fluorescence in situ hybridization (FISH), are challenging and low in efficiency, especially when karyotyping aneuploid and polyploid plants. The use of low coverage whole-genome resequencing (lcWGR) data for karyotyping was explored, but existing methods are complicated and require control samples. RESULTS: In this study, a new protocol for molecular karyotype analysis was provided, which proved to be a simpler, faster, and more accurate method, requiring no control. Notably, our method not only provided the copy number of each chromosome of an individual but also an accurate evaluation of the genomic contribution from its parents. Moreover, we verified the method through FISH and published resequencing data. CONCLUSIONS: This method is of great significance for species evolution analysis, chromosome engineering, crop improvement, and breeding.

Downregulation of the expression of subgenomic chromosome A7 genes promotes plant height in resynthesized allopolyploid Brassica napus.

KEY MESSAGE: Homoeolog expression bias and the gene dosage effect induce downregulation of genes on chromosome A7, causing a significant increase in the plant height of resynthesized allopolyploid Brassica napus. Gene expression levels in allopolyploid plants are not equivalent to the simple average of the expression levels in the parents and are associated with several non-additive expression phenomena, including homoeolog expression bias. However, hardly any information is available on the effect of homoeolog expression bias on traits. Here, we studied the effects of gene expression-related characteristics on agronomic traits using six isogenic resynthesized Brassica napus lines across the first ten generations. We found a group of genes located on chromosome A7 whose expression levels were significantly negatively correlated with plant height. They were expressed at significantly lower levels than their homoeologous genes, owing to allopolyploidy rather than inheritance from parents. Homoeolog expression bias resulted in resynthesized allopolyploids with a plant height similar to their female Brassica oleracea parent, but significantly higher than that of the male Brassica rapa parent. Notably, aneuploid lines carrying monosomic and trisomic chromosome A7 had the highest and lowest plant heights, respectively, due to changes in the expression bias of homoeologous genes because of alterations in the gene dosage. These findings suggest that the downregulation of the expression of homoeologous genes on a single chromosome can result in the partial improvement of traits to a significant extent in the nascent allopolyploid B. napus.

Genome-wide identification and gene expression analysis of the 14-3-3 gene family in potato (Solanum tuberosum L.).

BACKGROUND: 14-3-3 proteins are essential in regulating various biological processes and abiotic stress responses in plants. Although 14-3-3 proteins have been studied in model plants such as Arabidopsis thaliana and Oryza sativa, there is a lack of research on the 14-3-3 gene family in potatoes (Solanum tuberosum L.). RESULTS: A total of 18 14-3-3 genes encoding proteins containing a typical conserved PF00244 domain were identified by genome-wide analysis in potatoes. The St14-3-3 gene family members were unevenly distributed across the chromosomes, and gene structure analysis showed that gene length and intron number varied greatly among the members. Phylogenetic analysis of 14-3-3 proteins in potatoes and other plant species showed that they could be divided into two distinct groups (ε and non-ε). Members in the ε group tended to have similar exon-intron structures and conserved motif patterns. Promoter sequence analysis showed that the St14-3-3 gene promoters contained multiple hormone-, stress-, and light-responsive cis-regulatory elements. Synteny analysis suggested that segmental duplication events contributed to the expansion of the St14-3-3 gene family in potatoes. The observed syntenic relationships between some 14-3-3 genes from potato, Arabidopsis, and tomato suggest that they evolved from a common ancestor. RNA-seq data showed that St14-3-3 genes were expressed in all tissues of potatoes but that their expression patterns were different. qRT-PCR assays revealed that the expression levels of nearly all tested St14-3-3 genes were affected by drought, salt, and low-temperature stresses and that different St14-3-3 genes had different responses to these stresses. CONCLUSIONS: In summary, genome-wide identification, evolutionary, and expression analyses of the 14-3-3 gene family in potato were conducted. These results provide important information for further studies on the function and regulation of St14-3-3 gene family members in potatoes.

Identification of potato Lipid transfer protein gene family and expression verification of drought genes StLTP1 and StLTP7.

Lipid transfer proteins (LTPs) are widely distributed in plants and play an important role in the response to stress. Potato (Solanum tuberosum L.) is sensitive to a lack of water, and drought stress is one of the limiting factors for its yield. Therefore, mining candidate functional genes for drought stress and creating new types of potato germplasm for drought resistance is an effective way to solve this problem. There are few reports on the LTP family in potato. In this study, 39 members of the potato LTP family were identified. They were located on seven chromosomes, and the amino acid sequences encoded ranged from 101 to 345 aa. All 39 family members contained introns and had exons that ranged from one to four. Conserved motif analysis of potato LTP transcription factors showed that 34 transcription factors contained Motif 2 and Motif 4, suggesting that they were conserved motifs of potato LTP. Compared with the LTP genes of homologous crops, the potato and tomato (Solanum lycopersicum L.) LTPs were the mostly closely related. The StLTP1 and StLTP7 genes were screened by quantitative reverse transcription PCR combined with potato transcriptome data to study their expression in tissues and the characteristics of their responses to drought stress. The results showed that StLTP1 and StLTP7 were upregulated in the roots, stems, and leaves after PEG 6000 stress. Taken together, our study provides comprehensive information on the potato LTP family that will help to develop a framework for further functional studies.