[Investigation on reproductive characteristics of Polygonatum cyrtonema].

The study is aimed to investigate the reproductive biology characteristics of Polygonatum cyrtonema, especially including phenology, flower bud differentiation, flowering timing, floral traits, pollen vigor and stigma receptivity. The results showed that P. cyrtonema forms inflorescence before the leaves spread. In the wild, P. cyrtonema is mainly pollinated by insects such as bumblebees, with a seed setting rate of 65.12%. The seed setting rate of indoor single plant isolation or self-pollination enclosed by parchment paper bag is 0, indicating that it is self-incompatible. In Lin'an city, seedlings begin to emerge from mid-March to early April(the temperature is higher than 7.5 ℃), buds begin to emerge from the end of March to mid-April, and then undergo the full bloom stage from mid-to-late April, and the final flowering stage from the end of April to mid-May. The whole flowering period lasts 36 to 45 days. There are obvious differences in the phenology of different provenances. The flowers come into bloom from the base to the top along the aboveground main axis, which usually contain 4-22 inflorescences with(2-) 4-10(-21) flowers per inflorescence. The flowering pe-riod for a single plant is 26-38 days. The single flower lasts about 20-25 days from budding to opening and withers 2 days after pollination, and then the ovary will gradually expand. If unpollinated, it will continue to bloom for 3-5 days and then wither. Flower development period is significantly related to pollen vigor and stigma remittance. The pollen viability is the highest when the flower is fully opened with anthers gathering on the stigma, and the receptivity is the strongest when the stigma protrudes out of the perianth and secretes mucus. The fruits and seeds ripen in October, and proper shading can ensure the smooth development and maturity of the seeds. This study provides a basis for the hybrid breeding and seed production of P. cyrtonema.

[Genome-wide identification and expression analysis of CSLA gene family of Dendrobium catenatum].

Glucomannan is the key active ingredient of Dendrobium catenatum, and CSLA family is responsible for glucomannan biosynthesis. In order to systematically evaluate the CSLA family members of D. catenatum, the bioinformatics methods were performed for genome-wide identification of DcCSLA gene family members through the genomic data of D. catenatum downloaded from the NCBI database, and further analyses of their phylogenetic relationship, gene structure, protein conserved domains and motifs, promoter cis-elements and gene expression profiles in response to stresses. The results showed that D. catenatum contains 13 CSLA members, all of which contain 9-10 exons. In the evolutionary relationship, CSLA genes were clustered into 5 groups, DcCSLA genes were distributed in all branches. Among which the ancestral genes of groupI existed before the monocot-dicot divergence, and groupⅡ-Ⅴ only existed in the monocot plants, indicating that group Ⅰ represents the earliest origin group. CSLA proteins are characteristic of the signature CESA_CaSu_A2 domain. Their promoter regions contain cis elements related to stresses and hormones. Under different stress treatments, low temperature induces the expression of DcCSLA5 and inhibits the expression of DcCSLA3. Infection of Sclerotium delphinii inhibits DcCSLA3/4/6/8/9/10 expression. Under the treatment of jasmonic acid, DcCSLA11 expression was significantly up-regulated, and DcCSLA2/5/7/12/13 were significantly down-regulated. These results laid a foundation for further study on the function of DcCSLA genes in glucomannan biosynthesis and accumulation.

Genome-wide identification and expression profiling of SET DOMAIN GROUP family in Dendrobium catenatum.

BACKGROUND: Dendrobium catenatum, as a precious Chinese herbal medicine, is an epiphytic orchid plant, which grows on the trunks and cliffs and often faces up to diverse environmental stresses. SET DOMAIN GROUP (SDG) proteins act as histone lysine methyltransferases, which are involved in pleiotropic developmental events and stress responses through modifying chromatin structure and regulating gene transcription, but their roles in D. catenatum are unknown. RESULTS: In this study, we identified 44 SDG proteins from D. catenatum genome. Subsequently, comprehensive analyses related to gene structure, protein domain organization, and phylogenetic relationship were performed to evaluate these D. catenatum SDG (DcSDG) proteins, along with the well-investigated homologs from the model plants Arabidopsis thaliana and Oryza sativa as well as the newly characterized 42 SDG proteins from a closely related orchid plant Phalaenopsis equestris. We showed DcSDG proteins can be grouped into eight distinct classes (I~VII and M), mostly consistent with the previous description. Based on the catalytic substrates of the reported SDG members mainly in Arabidopsis, Class I (E(z)-Like) is predicted to account for the deposition of H3K27me2/3, Class II (Ash-like) for H3K36me, Class III (Trx/ATX-like) for H3K4me2/3, Class M (ATXR3/7) for H3K4me, Class IV (Su (var)-like) for H3K27me1, Class V (Suv-like) for H3K9me, as well as class VI (S-ET) and class VII (RBCMT) for methylation of both histone and non-histone proteins. RNA-seq derived expression profiling showed that DcSDG proteins usually displayed wide but distinguished expressions in different tissues and organs. Finally, environmental stresses examination showed the expressions of DcASHR3, DcSUVR3, DcATXR4, DcATXR5b, and DcSDG49 are closely associated with drought-recovery treatment, the expression of DcSUVH5a, DcATXR5a and DcSUVR14a are significantly influenced by low temperature, and even 61% DcSDG genes are in response to heat shock. CONCLUSIONS: This study systematically identifies and classifies SDG genes in orchid plant D. catenatum, indicates their functional divergence during the evolution, and discovers their broad roles in the developmental programs and stress responses. These results provide constructive clues for further functional investigation and epigenetic mechanism dissection of SET-containing proteins in orchids.

[Occurrence regularity of Dendrobium catenatum southern blight disease].

In order to scientifically prevent and control Dendrobium catenatum southern blight disease,the main factors related to this disease occurrence,the pathogen( Sclerotium delphinii),environmental factors( temperature and humidity) and D. catenatum germplasms,were investigated. The results showed that reaching 25-30 ℃ temperature and over 95% humidity simultaneously should be the main conditions for the occurrence and prevalence of D. catenatum southern blight disease. Moreover,the S. delphinii-infected plants and their contaminated substrates were the disease spreading sources. Therefore,removing the infected plants,dealing with the contaminated substrates,keeping air ventilation,and reducing air humidity are the effective ways to prevent and control the occurrence and prevalence of D. catenatum southern blight disease. The research also indicated that D. catenatum has different resistances to the southern blight disease depending on germplasm. The present study lays important foundations for the breeding of D. catenatum diseaseresistant varieties and the further analysis of the infection and resistance mechanisms underlying southern blight disease.