Vegetation restoration has been widely used in karst rocky desertification (KRD) areas of southwestern China, but the response of microbial community to revegetation has not been well characterized. We investigated the diversity, structure, and co-occurrence patterns of bacterial communities in soils of five vegetation types (grassland, shrubbery, secondary forest, pure plantation and mixed plantation) in KRD area using high-throughput sequencing of the 16S rRNA gene. Bray-Curtis dissimilarity analysis revealed that 15 bacterial community samples were clustered into five groups that corresponded very well to the five vegetation types. Shannon diversity was positively correlated with pH and Ca2+ content but negatively correlated with organic carbon, total nitrogen, and soil moisture. Redundancy analysis indicated that soil pH, Ca2+ content, organic carbon, total nitrogen, and soil moisture jointly influenced bacterial community structure. Co-occurrence network analysis revealed non-random assembly patterns of bacterial composition in the soils. Bryobacter, GR-WP33-30, and Rhizomicrobium were identified as keystone genera in co-occurrence network. These results indicate that diverse soil physicochemical properties and potential interactions among taxa during vegetation restoration may jointly affect the bacterial community structure in KRD regions.
Background
As a perennial crop, oil-Camellia possesses a long domestication history and produces high-quality seed oil that is beneficial to human health. Camellia oleifera Abel. is a sister species to the tea plant, which is extensively cultivated for edible oil production. However, the molecular mechanism of the domestication of oil-Camellia is still limited due to the lack of sufficient genomic information.
Results
To elucidate the genetic and genomic basis of evolution and domestication, here we report a chromosome-scale reference genome of wild oil-Camellia (2.95 Gb), together with transcriptome sequencing data of 221 cultivars. The oil-Camellia genome, assembled by an integrative approach of multiple sequencing technologies, consists of a large proportion of repetitive elements (76.1%) and high heterozygosity (2.52%). We construct a genetic map of high-density corrected markers by sequencing the controlled-pollination hybrids. Genome-wide association studies reveal a subset of artificially selected genes that are involved in the oil biosynthesis and phytohormone pathways. Particularly, we identify the elite alleles of genes encoding sugar-dependent triacylglycerol lipase 1, β-ketoacyl-acyl carrier protein synthase III, and stearoyl-acyl carrier protein desaturases; these alleles play important roles in enhancing the yield and quality of seed oil during oil-Camellia domestication.
Conclusions
We generate a chromosome-scale reference genome for oil-Camellia plants and demonstrate that the artificial selection of elite alleles of genes involved in oil biosynthesis contributes to oil-Camellia domestication.
Pecan (Carya illinoinensis) is an important tree nut throughout the world. The high concentration of flavonoid in its kernels makes it an excellent food with health benefits. However, the molecular basis of flavonoid biosynthesis in pecan remains unclear, which hinders quality breeding in this plant. Therefore, in order to find the crucial genes involved in flavonoid biosynthesis, the changes in flavonoid profiles and the transcriptomes of pecan kernels at four developmental stages (late water, gel, dough, and mature stages) were analyzed. As a result, the highest levels of total phenolic, condensed tannin, and flavan-3-ols were observed at the "late water stage". Catechin was the most abundant flavan-3-ol at different development stages. In total, 64 773 unigenes were obtained, and 46 924 (72.44%) unigenes were annotated. After differentially expressed gene (DEG) analysis, 12 750 unique DEGs were identified. Flavonoid-related DEGs of 36 structural genes and eight MYBs were obtained. The structural gene set contained three PALs, three CHSs, two CHIs, one F3H, two F3′Hs, two F3′5′Hs, one DFR, one ANS, two LARs, and two ANRs. The expression patterns of most of the structural genes were consistent with the changes in flavonoid profiles during kernel development. We believe that this RNA-Seq data set will provide valuable resources for unraveling the molecular mechanism of flavonoid metabolism in pecan and will significantly promote genetic studies and quality breeding in this plant.
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