Genome-wide transcriptome analysis reveals molecular pathways involved in leafy head formation of Chinese cabbage(Brassica rapa)

Chinese cabbage plants go through seedling and rosette stages before forming their leafy head.Chinese cabbage plants resemble pak-choi plants at their seedling stage,but in their rosette stage the leaves of Chinese cabbage differentiate,as they increase in size with shorter petioles.In order to understand the molecular pathways that play a role in leafy head formation,transcript abundance of young emerging leaves was profiled during development of two Chinese cabbage genotypes and a single pak-choi genotype.The two Chinese cabbages differed in many aspects,among others earliness,leaf size and shape,leaf numbers,and leafy head shape.Genome-wide transcriptome analysis clearly separated the seedling stages of all three genotypes together with the later stages from pak-choi,from the later developmental stages of both Chinese cabbages(rosette,folding,and heading).Weighted correlation network analysis and hierarchical clustering using Euclidean distances resulted in gene clusters with transcript abundance patterns distinguishing the two Chinese cabbages from pak-choi.Three clusters included genes with transcript abundance affected by both genotype and developmental stage,whereas two clusters showed only genotype effects.This included a genotype by developmental stage cluster highly enriched with the MapMan category photosynthesis,with high expression during rosette and folding in Chinese cabbages and low expression in the heading inner leaves that are not exposed to light.The other clusters contained many genes in the MapMan categories Cell,showing again differences between pak-choi and both Chinese cabbages.We discuss how this relates to the differences in leaf blade growth between Chinese cabbage and pak-choi,especially at the rosette stage.Overall,comparison of the transcriptome between leaves of two very different Chinese cabbages with pak-choi during plant development allowed the identification of specific gene categories associated with leafy head formation.

Genetic regulators of leaf size in Brassica crops

Leaf size influences plant development and biomass and is also an important agricultural trait in Brassica crops,in which leaves are the main organ produced for consumption.Leaf size is determined by the coordinated regulation of cell proliferation and cell expansion during leaf development,and these processes are strictly controlled by various integrated signals from the intrinsic regulatory network and the growth environment.Understanding the molecular mechanism of leaf size control is a prerequisite for molecular breeding for crop improvement purposes.Although research on leaf size control is just beginning in Brassica,recent studies have identified several genes and QTLs that are important in leaf size regulation.These genes have been proposed to influence leaf growth through different pathways and mechanisms,including phytohormone biosynthesis and signaling,transcription regulation,small RNAs,and others.In this review,we summarize the current findings regarding the genetic regulators of leaf size in Brassica and discuss future prospects for this research.

Genetic analysis of the “head top shape” quality trait of Chinese cabbage and its association with rosette leaf variation

The agricultural and consumer quality of Chinese cabbage is determined by its shape.The shape is defined by the folding of the heading leaves,which defines the head top shape(HTS).The overlapping HTS,in which the heading leaves curve inward and overlap at the top,is the shape preferred by consumers.To understand the genetic regulation of HTS,we generated a large segregating F 2 population from a cross between pak choi and Chinese cabbage,with phenotypes ranging from nonheading to heading with either outward curving or inward curving overlapping heading leaves.HTS was correlated with plant height,outer/rosette leaf length,and petiole length.A high-density genetic map was constructed.Quantitative trait locus(QTL)analysis resulted in the identification of 22 QTLs for leafy head-related traits,which included five HTS QTLs.Bulked segregant analysis(BSA)was used to confirm HTS QTLs and identify candidate genes based on informative single-nucleotide polymorphisms.Interestingly,the HTS QTLs colocalized with QTLs for plant height,outer/rosette leaf,and petiole length,consistent with the observed phenotypic correlations.Combined QTL analysis and BSA laid a foundation for molecular marker-assisted breeding of Chinese cabbage HTS and directions for further research on the genetic regulation of this trait.

Reusable salt-template strategy for synthesis of porous nitrogen-rich carbon boosts H_(2)S selective oxidation

Removing hydrogen sulfide(H_(2)S)via the selective oxidation has been considered an effective way to further purify the indusial sulfurcontaining due to it can completely transform residual H_(2)S into elemental sulfur.While N-doped porous carbon was applied to H_(2)S selective oxidation,a sustainable methodology for the synthesis of efficient and stable N-doped carbon catalysts remains a difficulty,limiting its future development in large-scale applications.Herein,we present porous,honeycomb-like N-doped carbon catalysts with large specific surface areas,high pyridinic N content,and numerous structural defects for H_(2)S selective oxidation prepared using reusable NaCl as the template.The asprepared NC-10-800 catalyst exhibits excellent catalytic performance(sulfur formation rate of 784 g_(sulfur) kg_(cat.)^(-1) h^(-1)),outstanding stability(>100 h),and excellent anti-water vapor,anti-CO_(2) and anti-oxidation properties,suggesting significant potential for practical industrial application.The characterization results and kinetic study demonstrate that the large surface areas and structural defects created by the molten salt at high temperature enhance the exposure of pyridinic N sites and thus accelerate the catalytic activity.Importantly,the water-soluble NaCl template could be easily washed from the carbon nanomaterials,and thus the downstream salt-containing wastewater could be subsequently reused for the dissolution of carbon precursors.This environment-friendly,low-cost,reusable salt-template strategy has significant implications for the development of N-doped carbon catalysts for practical applications.

Construction of a high-density mutant population of Chinese cabbage facilitates the genetic dissection of agronomic traits

Chinese cabbage(Brassica rapa ssp.pekinensis)is an economically important vegetable crop throughout the world,especially in Asia.High-quality genome sequences are available for Chinese cabbage,but gene functional studies remain challenging.To promote functional genomic studies of Chinese cabbage,we generated an ethyl methane sulfonate(EMS)mutant population of~8000 M_(2) plants using the double haploid inbred line A03 as the parent.The genome of A03 was sequenced and used as a reference for high-throughput functional characterization of gene mutations at the whole-genome level.A total of 300 M_(2) to M_(5) EMS mutants were phenotypically screened and then sequenced,revealing 750629 SNPs and 46272 InDel mutations that cover 98.27%of all predicted genes in the A03 genome.A forward-genetics approach was successfully used to identify two genes with chloroplast-related functions that are responsible for the yellow leaf mutant trait.A reverse-genetics approach was also used to identify associations between mutations in five genes of the glucosinolate biosynthetic pathway and variations in glucosinolate content of the mutant plants.In addition,we built the Chinese cabbage EMS mutation database(CCEMD,www.bioinformaticslab.cn/EMSmutation/home)to increase the usability of this mutant population resource.In summary,we performed large-scale screening of a heading Chinese cabbage EMS mutant collection at the phenotypic and genotypic levels,which will facilitate gene mining of Chinese cabbage and might also be useful for the study of other Brassica crops.