Mass spectrometry imaging and single-cell transcriptional profiling reveal the tissue-specific regulation of bioactive ingredient biosynthesis in Taxus leaves

Taxus leaves provide the raw industrial materials for taxol,a natural antineoplastic drug widely used in the treatment of various cancers.However,the precise distribution,biosynthesis,and transcriptional regulation of taxoids and other active components in Taxus leaves remain unknown.Matrix-assisted laser desorption/ionization–mass spectrometry imaging analysis was used to visualize various secondary metabolites in leaf sections of Taxus mairei,confirming the tissue-specific accumulation of different active metabolites.Single-cell sequencing was used to produce expression profiles of 8846 cells,with a median of 2352 genes per cell.Based on a series of cluster-specific markers,cells were grouped into 15 clusters,suggesting a high degree of cell heterogeneity in T.mairei leaves.Our data were used to create the first Taxus leaf metabolic single-cell atlas and to reveal spatial and temporal expression patterns of several secondary metabolic pathways.According to the cell-type annotation,most taxol biosynthesis genes are expressed mainly in leaf mesophyll cells;phenolic acid and flavonoid biosynthesis genes are highly expressed in leaf epidermal cells(including the stomatal complex and guard cells);and terpenoid and steroid biosynthesis genes are expressed specifically in leaf mesophyll cells.A number of novel and cell-specific transcription factors involved in secondary metabolite biosynthesis were identified,including MYB17,WRKY12,WRKY31,ERF13,GT_2,and bHLH46.Our research establishes the transcriptional landscape of major cell types in T.mairei leaves at a single-cell resolution and provides valuable resources for studying the basic principles of cell-type-specific regulation of secondary metabolism.

基于SSR分子标记的酸浆属植物亲缘关系研究

近年来,由于营养价值高、果实可当水果食用且具有潜在的药用价值,酸浆属(Physalis)植物在全球范围内受到了越来越多的关注。采用SSR分子标记技术对我国范围内主要分布的4种酸浆属植物的22份样品进行了亲缘关系研究,结果表明,20对SSR引物共扩增出118个位点,其中107个(90.7%)为多态性位点;平均种间遗传相似系数为0.501。UPGMA聚类和PCoA分析结果得出相似结论,并且将供试酸浆属植物样品分为两大类。其中,酸浆(P.alkekengi var.francheti)的所有样品与其它酸浆属植物的遗传距离最远,单独聚为一类,与前人的研究结果非常吻合。研究表明,SSR标记遗传信息丰富,可以用于酸浆属植物的亲缘关系分析。研究结果为酸浆属种质资源保护提供了有效信息,并且为酸浆属植物的分子辅助育种奠定了重要基础。

The linkage maps of Dendrobium species based on RAPD and SRAP markers

Dendrobium plants are used commonly as tonic herbs and health food in many Asian countries,especially in China.Here we report the genetic map construction of two Dendrobium species with a double pseudo-testcross strategy using random amplified polymorphic DNA(RAPD) and sequence-related amplified polymorphism(SRAP) markers.A F1 mapping population of 90 individuals was developed from a cross between D.officinale and D.hercoglossum.A total of 307 markers,including 209 RAPD and 98 SRAP,were identified and used for genetic linkage group(LG) analysis.The D.officinale linkage map consisted of 11 major linkage groups and 3 doublets,which covered 629.4 cM by a total of 62 markers with an average locus distance of 11.2 cM between two adjacent markers.The D.hercoglossum linkage map contained 112 markers mapped on 15 major and 4 minor linkage groups,spanning a total length of 1,304.6 cM with an average distance of 11.6 cM between two adjacent markers.The maps constructed in this study covered 92.7% and 82.7% of the D.hercoglossum and D.officinale genomes respectively,providing an important basis for the mapping of horticultural and medicinal traits and for the application of marker-assisted selection in Dendrobium breeding program.

Genome-wide identification, expression analysis of auxin-responsive GH_3 family genes in maize(Zea mays L.) under abiotic stresses

Auxin is involved in different aspects of plant growth and development by regulating the expression of auxinresponsive family genes. As one of the three major auxinresponsive families, GH3(Gretchen Hagen3) genes participate in auxin homeostasis by catalyzing auxin conjugation and bounding free indole-3-acetic acid(IAA) to amino acids.However, how GH3 genes function in responses to abiotic stresses and various hormones in maize is largely unknown.Here, the latest updated maize(Zea mays L.) reference genome sequence was used to characterize and analyze the Zm GH3 family genes from maize. The results showed that 13 Zm GH3 genes were mapped on fi ve maize chromosomes(total10 chromosomes). Highly diversi fi ed gene structures and tissue-speci fi c expression patterns suggested the possibility of function diversi fi cation for these genes in response to environmental stresses and hormone stimuli. The expression patterns of Zm GH3 genes are responsive to several abiotic stresses(salt, drought and cadmium) and major stress-relatedhormones(abscisic acid, salicylic acid and jasmonic acid)Various environmental factors suppress auxin free IAA contents in maize roots suggesting that these abiotic stresses and hormones might alter GH3-mediated auxin levels. The respon siveness of Zm GH3 genes to a wide range of abiotic stresses and stress-related hormones suggested that Zm GH3 s are involved in maize tolerance to environmental stresses.