[学术文献] Genome-wide association study reveals new genes involved in leaf trichome formation in polyploid oilseed rape (Brassica napus L.) 进入全文
Plant Cell Environ
Leaf trichomes protect against various biotic and abiotic stresses in plants. However, there is little knowledge about this trait in oilseed rape (Brassica napus). Here, we demonstrated that hairy leaves were less attractive to Plutella xylostella larvae than glabrous leaves. We established a core germplasm collection with 290 accessions for a genome-wide association study (GWAS) of the leaf trichome trait in oilseed rape. We compared the transcriptomes of the shoot apical meristem (SAM) between hairy- and glabrous-leaf genotypes to narrow down the candidate genes identified by GWAS. The single nucleotide polymorphisms and the different transcript levels of BnaA.GL1.a, BnaC.SWEET4.a, BnaC.WAT1.a and BnaC.WAT1.b corresponded to the divergence of the hairy- and glabrous-leaf phenotypes, indicating the role of sugar and/or auxin signalling in leaf trichome initiation. The hairy-leaf SAMs had lower glucose and sucrose contents but higher expression of putative auxin responsive factors than the glabrous-leaf SAMs. Spraying of exogenous auxin (8 μm) increased leaf trichome number in certain genotypes, whereas spraying of sucrose (1%) plus glucose (6%) slightly repressed leaf trichome initiation. These data contribute to the existing knowledge about the genetic control of leaf trichomes and would assist breeding towards the desired leaf surface type in oilseed rape.
[学术文献] Dissection of genetic architecture for glucosinolate accumulations in leaves and seeds of Brassica napus by genome-wide association study 进入全文
Plant Biotechnology Journal
Glucosinolates (GSLs), whose degradation products have been shown to be increasingly important for human health and plant defence, compose important secondary metabolites found in the order Brassicales. It is highly desired to enhance pest and disease resistance by increasing the leaf GSL content while keeping the content low in seeds of Brassica napus, one of the most important oil crops worldwide. Little is known about the regulation of GSL accumulation in the leaves. We quantified the levels of 9 different GSLs and 15 related traits in the leaves of 366 accessions and found that the seed and leaf GSL content were highly correlated (r=0.79). A total of 78 loci were associated with GSL traits, and five common and eleven tissue-specific associated loci were related to total leaf and seed GSL content. Thirty-six candidate genes were inferred to be involved in GSL biosynthesis. The candidate gene BnaA03g40190D(BnaA3.MYB28) was validated by DNA polymorphisms and gene expression analysis. This gene was responsible for high leaf/low seed GSL content and could explain 30.62% of the total leaf GSL variation in the low seed GSL panel and was not fixed during double-low rapeseed breeding. Our results provide new insights into the genetic basis of GSL variation in leaves and seeds and may facilitate the metabolic engineering of GSLs and the breeding of high leaf/low seed GSL content in B. napus.
[学术文献] Drivers of metabolic diversification: how dynamic genomic neighbourhoods generate new biosynthetic pathways in the Brassicaceae 进入全文
Plants produce an array of specialized metabolites with important ecological functions. The mechanisms underpinning the evolution of new biosynthetic pathways are not well-understood. Here, we exploit available genome sequence resources to investigate triterpene biosynthesis across the Brassicaceae. #1; Oxidosqualene cyclases (OSCs) catalyze the first committed step in triterpene biosynthesis. Systematic analysis of 13 sequenced Brassicaceae genomes was performed to identify all OSC genes. The genome neighbourhoods (GNs) around a total of 163 OSC genes were investigated to identify Pfam domains significantly enriched in these regions. All-vs-all comparisons of OSC neighbourhoods and phylogenomic analysis were used to investigate the sequence similarity and evolutionary relationships of the numerous candidate triterpene biosynthetic gene clusters (BGCs) observed. Functional analysis of three representative BGCs was carried out and their triterpene pathway products were elucidated. #1; Our results indicate that plant genomes are remarkably plastic, and that dynamic GNs generate new biosynthetic pathways in different Brassicaceae lineages by shuffling the genes encoding a core palette of triterpene-diversifying enzymes, presumably in response to strong environmental selection pressure. #1; These results illuminate a genomic basis for diversification of plant-specialized metabolism through natural combinatorics of enzyme families, which can be mimicked using synthetic biology to engineer diverse bioactive molecules.
New genes often drive the evolution of gene interaction networks. In Brassica napus, the widely used genic male sterile breeding system 7365ABC is controlled by two young genes, Bnams4b and BnaMs3. However, the interaction mechanism of these two young genes remains unclear. #1; Here, we confirmed that Bnams4b interacts with the nuclear localised E3 ligase BRUTUS (BTS). Ectopic expression of AtBRUTUS (AtBTS) and comparison between Bnams4b-transgenic Arabidopsis and bts mutants suggested that Bnams4b may drive translocation of BTS to cause various toxic defects. #1; BnaMs3 gained an exclusive interaction with the plastid outer-membrane translocon Toc33 compared with Bnams3 and AtTic40, and specifically compensated for the toxic effects of Bnams4b . Heat shock treatment also rescued the sterile phenotype, and high temperature suppressed the interaction between Bnams4b and BTS in yeast. Furthermore, the ubiquitin system and TOC (translocon at the outer envelope membrane of chloroplasts) component accumulation were affected in Bnams4b-transgenic Arabidopsis plants. #1; Taken together, these results indicate that new chimeric Bnams4b carries BTS from nucleus to chloroplast, which may disrupt the normal ubiquitin-proteasome system to cause toxic effects, and these defects can be compensated by BnaMs3-Toc33 interaction or environmental heat shock. It reveals a scenario in which two population-specific coevolved young genes reshape a novel interaction network in plants.
[学术文献] Distinct patterns of microbial metabolic fingerprints in sows and their offspring: a pilot study 进入全文
Microbial metabolism and growth in the intestinal tract depend on the composition of substrates present in the digesta and their ability to be metabolised by the microorganisms. The aim of this pilot study was to characterise potential hindgut microbial activity during perinatal period in sows and their offspring. Rectal samples from three sows (1–3 weeks before and after birth) and three of their piglets (1–5 weeks after birth), were subjected to assays using BIOLOG GEN III microplates to produce metabolic fingerprints for each animal. The number of metabolised substrates of the sow hindgut microbiota was stable during the pregnancy and lactation periods, as assessed by the richness index. In piglets, the richness was stable during the suckling period and at beginning of weaning, however, it decreased when the piglets were 5 weeks old ( P ≤ 0.05). Analysis of associations between the sows and the piglets and the microbial metabolic potential showed that microbial metabolism was strongly associated with the catabolism of carbohydrates especially in sows. Only 5-week-old weaned piglets clustered together with the sows regarding the microbial catabolism of substrates, but not suckling piglets. The association analyses clustered all the piglets in two groups distinctive for litter. The analysis of metabolic fingerprints via microbial growth with different substrates can be useful to positively influence microbial community function such as selectively enhancing desirable active microbial populations to benefit health of the gut and the animal.