Expansins are extracellular proteins that are involved in cell wall modifications such as cell wall disassembly, cell separation, and cell expansion. Little is known about expansin gene expression during flower development of wintersweet (Chimonanthus praecox). In the present study, an expansin gene, CpEXP1, was isolated from the wintersweet flower cDNA library through random sequencing; this gene encodes a putative protein of 257 amino acids with the essential features conserved, like in other alpha expansins. The CpEXP1 gene exhibited different transcription levels in different tissues and had a significantly higher expression in flowers than other tissues. It is strongly correlated with the development of the flower. The expression of CpEXP1 increased in the flower buds or whole flowers from Stage 1 to 4 and decreased from Stage 5 to 6 during natural opening. Ethephon (an ethylene releaser) treatment promoted cut flower senescence, whereas 1-methylcyclopropene (1-MCP) (an ethylene perception inhibitor) delayed the process of flower wilting. This result is associated with the concomitant lower transcript levels of CpEXP1 in the ethephon-treated samples as well as the steady expression in the 1-MCP-treated samples compared with that in control flowers. The studies show the interesting observation that the expression of an expansin gene CpEXP1 is correlated with the development of Chimonanthus praecox flowers, the upregulation during flower opening vs. the downregulation during senescence.
Jing Ma, Zheng Li, Bin Wang, Shunzhao Sui and Mingyang Li
Zhe Cao, Shunzhao Sui, Qian Yang and Zhanao Deng
A number of caladium cultivars (Caladium ×hortulanum), including Miss Muffet and Gingerland, produce rugose leaves. The rugosity on these leaves is an intriguing characteristic, often resulting in an increased ornamental value. This study was conducted to understand the mode of inheritance of this trait and to determine its genetic relationship with other foliar characteristics including leaf shape, main vein color, and leaf spotting in caladiums. Sixteen caladium cultivars/breeding lines were crossed and 20 populations were produced; progeny of these populations were phenotyped for rugose leaf as well as leaf shape, main vein color, and leaf spotting. Results showed that a single locus with two alleles controlled the presence or absence of rugose leaves in these populations. The locus was designated as RLF, with the dominant RLF allele for rugose leaves and the recessive allele rlf for nonrugose (flat) leaves. Rugose cultivars Miss Muffet and Gingerland and breeding line UF-317 possessed the heterozygous genotype RLFrlf. Rugose leaf was inherited independently from leaf shape, but linked with the green main vein allele (V g) at the V locus and the leaf spotting allele (S) at the S locus. Three-point analysis of the segregation of the three linked traits in reciprocal crosses between ‘Miss Muffet’ and nonrugose ‘Candidum’ indicated a genetic linkage map with the gene order of S locus locating between the V and the RLF loci. The information obtained from this study will be useful for developing breeding strategies for producing new caladium cultivars with or without rugose leaves, and can facilitate the understanding of the mode of inheritance for rugose leaves in other aroids and other plants.
Renwei Huang, Daofeng Liu, Min Zhao, Zhineng Li, Mingyang Li and Shunzhao Sui
Lobularia maritima (L.) Desv. is an important ornamental plant. We investigated an efficient method to induce tetraploid plants of L. maritima (L.) Desv. by treating germinating seeds and apical growing points of seedlings with a range of concentrations of colchicine for different periods of time. Examination of the ploidy level by counting chromosome numbers at metaphase confirmed that the chromosome number of diploid plants was 2n = 2x = 24, whereas 2n = 4x = 48 was observed in tetraploid plants. The morphological characteristics of the diploid and colchicine-induced tetraploid plants were compared. Increases in the size of leaves, flowers, and stomata were observed in the tetraploid plants compared with the diploids. However, the stomatal density and plant height of the tetraploid plants were lower than for the diploid plants. This study presents the first report of autotetraploid plants of L. maritima (L.) Desv., and of the successful generation of tetraploid plants with improved ornamental traits by colchicine treatment.
Shunzhao Sui, Jianghui Luo, Daofeng Liu, Jing Ma, Weiting Men, Lu Fan, Yu Bai and Mingyang Li
Wintersweet (Chimonanthus praecox) is a woody garden plant with fragrant flowers, which blooms in deep winter. The vase life of fresh cut flowers is 8–9 days. We applied ethylene and 1-methylcyclopropene (1-MCP; an ethylene action inhibitor) to test the role of ethylene in flower opening and senescence. In addition, abscisic acid (ABA), gibberellic acid (GA3), two cytokinins, 6-benzylaminopurine (6-BA), and zeatin (ZT) were also applied. The expression pattern of CpSRG1, a senescence-related gene, was analyzed. Ethylene treatment accelerated flower opening and senescence, decreasing vase life by 2.1 days. It also decreased flower break strength, indicating the induction of abscission. 1-MCP slowed opening, delayed senescence, and prolonged vase life by 2.6 days. Ethylene dramatically induced the expression of the CpSRG1 gene, while 1-MCP suppressed it. ZT promoted flower opening and increased vase life by 1.6 days. It suppressed the expression of CpSRG1. 6-BA, GA3, or ABA had no significant effect on flower opening and senescence of wintersweet.
Rui Li, Lu Fan, Jingdong Lin, Mingyang Li, Daofeng Liu and Shunzhao Sui
Kalanchoe (Kalanchoe blossfeldiana) is a common potted flower that is popular throughout the world. Brown spot (caused by Stemphylium lycopersici) is one of the common foliage diseases in kalanchoe. This disease tends to infect leaves of kalanchoe plants in hot and humid environments, reducing their aesthetic value. The current investigation aimed to generate mutations resistant to brown spot in ‘Mary’ kalanchoe through chemical mutagenesis followed by molecular marker identification. Putative mutants were developed by treating embryogenic calluses with ethyl methanesulfonate (EMS) at median lethal doses (LD50)–either a 0.8% concentration for 2 hours or a 1.0% concentration for 0.5 hours. Brown spot crude toxin solution was used as the selection agent to identify disease-resistant calluses during tissue culture. The optimal crude concentration (60%) was determined by soaking calluses with different concentrations of crude pathogen: 0%, 20%, 40%, 60%, and 80% (v/v). A total of 32 anti-brown spot lines were regenerated and tested for disease resistance with detached leaves. Three regenerated EMS mutant lines showed no obvious brown spot lesions on their leaves after the disease resistance assay and were subjected to polymorphism identification by start codon targeted (SCoT) molecular markers. Three (SCoT40, SCoT71, and SCoT72) of 45 selected primers were chosen to identify the mutants. This work may lay the foundation for further development of new disease-resistant cultivars of kalanchoe.
Daofeng Liu, Jing Ma, Jianfeng Yang, Tien V. Nguyen, Huamin Liu, Renwei Huang, Shunzhao Sui and Mingyang Li
Wintersweet is a woody ornamental plant and has a long history of human cultivation. Few molecular markers have been characterized and remain scant in wintersweet. This study aimed to mine simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs) from the transcriptomic database of wintersweet. A total of 3972 SSRs and 97,060 putative SNPs/indels (92,307 SNPs and 4753 indels) were identified in this data set. This study marks the highest number of SSR and SNP markers discovered to date from wintersweet by using transcriptome sequencing data. These identified markers will provide a useful source for molecular genetic studies such as genetic diversity and characterization, association mapping, and map-based gene cloning in wintersweet.