RFLP and AFLP analysis of inter- and intraspecific variation of Brassica rapa and B. napus shows that B. rapa is an important genetic resource for B. napus improvement

Transcriptome Shock in Developing Embryos of a Brassica napus and Brassica rapa Hybrid

Interspecific crosses that fuse the genomes of two different species may result in overall gene expression changes in the hybrid progeny, called 'transcriptome shock'. To better understand the expression pattern after genome merging during the early stages of allopolyploid formation, we performed RNA sequencing analysis on developing embryos of Brassica rapa, B. napus, and their synthesized allotriploid hybrids. Here, we show that the transcriptome shock occurs in the developing seeds of the hybrids. Of the homoeologous gene pairs, 17.1% exhibit expression bias, with an overall expression bias toward B. rapa. The expression level dominance also biases toward B. rapa, mainly induced by the expression change in homoeologous genes from B. napus. Functional enrichment analysis revealed significant differences in differentially expressed genes (DEGs) related to photosynthesis, hormone synthesis, and other pathways. Further study showed that significant changes in the expression levels of the key transcription factors (TFs) could regulate the overall interaction network in the developing embryo, which might be an essential cause of phenotype change. In conclusion, the present results have revealed the global changes in gene expression patterns in developing seeds of the hybrid between B. rapa and B. napus, and provided novel insights into the occurrence of transcriptome shock for harnessing heterosis.

Amplified Fragment Length Polymorphism: Applications and Recent Developments

AFLP or amplified fragment length polymorphism is a PCR-based molecular technique that uses selective amplification of a subset of digested DNA fragments from any source to generate and compare unique fingerprints of genomes. It is more efficient in terms of time, economy, reproducibility, informativeness, resolution, and sensitivity, compared to other popular DNA markers. Besides, it requires very small quantities of DNA and no prior genome information. This technique is widely used in plants for taxonomy, genetic diversity, phylogenetic analysis, construction of high-resolution genetic maps, and positional cloning of genes, to determine relatedness among cultivars and varietal identity, etc. The review encompasses in detail the various applications of AFLP in plants and the major advantages and disadvantages. The review also considers various modifications of this technique and novel developments in detection of polymorphism. A wet-lab protocol is also provided.

Characterization and expression profiles of miRNAs in the triploid hybrids of Brassica napus and Brassica rapa

BACKGROUND

Polyploidy provides a means of interspecific genome transfer to incorporate preferable traits from progenitor to progeny. However, few studies on miRNA expression profiles of interspecific hybrids of B. napus (AnAnCnCn) and B. rapa (ArAr) have been reported.

RESULTS

Here, we apply small RNA sequencing to explore miRNA expression patterns between B. napus, B. rapa and their F1 hybrid. Bioinformatics analysis identified 376, 378, 383 conserved miRNAs and 82, 76, 82 novel miRNAs in B. napus, B. rapa and the F1 hybrid, respectively. Moreover, 213 miRNAs were found to be differentially expressed between B. napus, B. rapa and the F1 hybrid. The present study also shows 211 miRNAs, including 77 upregulated and 134 downregulated miRNAs, to be nonadditively expressed in the F1 hybrid. Furthermore, miRNA synteny analysis revealed high genomic conservation between the genomes of B. napus, B. rapa and their F1 hybrid, with some miRNA loss and gain events in the F1 hybrid.

CONCLUSIONS

This study not only provides useful resources for exploring global miRNA expression patterns and genome structure but also facilitates genetic research on the roles of miRNAs in genomic interactions of Brassica allopolyploids.