Regulation of phenylpropanoid biosynthesis by MdMYB88 and MdMYB124 contributes to pathogen and drought resistance in apple

MdMYB88 and MdMYB124 have been demonstrated to be responsible for lignin accumulation in apple under drought stress.In this study,using a metabolomic approach,we identified differentially accumulated phenylpropanoid and flavonoid metabolites in MdMYB88/124 transgenic RNAi plants under control and long-term drought stress conditions in apple roots.We confirmed the regulation of phenylalanine by MdMYB88 and MdMYB124 via UPLC-MS in apple roots under both control and drought conditions.Using Electrophoretic Mobility Shift Assay(EMSA)and ChIPquantitative PCR(qPCR)analyses,we found that MdMYB88 positively regulates the MdCM2 gene,which is responsible for phenylalanine biosynthesis,through binding to its promoter region.Under long-term drought conditions,MdMYB88/124 RNAi plants consistently accumulated increased amounts of H2O2 and MDA,while MdMYB88 and MdMYB124 overexpression plants accumulated decreased amounts of H2O2 and MDA.We also examined the accumulation of metabolites in the phenylpropanoid biosynthesis pathway in the leaves of MdMYB88 and MdMYB124 transgenic apple plants after long-term drought stress.We found that metabolites responsible for plant defense,including phenylpropanoids and flavonoids,accumulated less in the RNAi plants but more in the overexpression plants under both control and drought conditions.We further demonstrated that MdMYB88/124 RNAi plants were more sensitive to Alternaria alternata f.sp.mali and Valsa mali,two pathogens that currently severely threaten apple production.In contrast,MdMYB88 and MdMYB124 overexpression plants were more tolerant to these pathogens.The cumulative results of this study provided evidence for secondary metabolite regulation by MdMYB88 and MdMYB124,further explained the molecular roles of MdMYB88 and MdMYB124 in drought resistance,and provided information concerning molecular aspects of their roles in disease resistance.

Genome-wide identification of droughtresponsive microRNAs in two sets of Malus from interspecific hybrid progenies

Drought stress can negatively impact apple fruit quality and yield.Apple microRNAs(miRNAs)participate in apple tree and fruit development,as well as in biotic stress tolerance;however,it is largely unknown whether these molecules are involved in the drought response.To identify drought-responsive miRNAs in Malus,we first examined the drought stress tolerance of ten F1 progenies of R3(M.×domestica)×M.sieversii.We performed Illumina sequencing on pooled total RNA from both drought-tolerant and drought-sensitive plants.The sequencing results identified a total of 206 known miRNAs and 253 candidate novel miRNAs from drought-tolerant plants and drought-sensitive plants under control or drought conditions.We identified 67 miRNAs that were differentially expressed in drought-tolerant plants compared with drought-sensitive plants under drought conditions.Under drought stress,61 and 35 miRNAs were differentially expressed in drought-tolerant and drought-sensitive plants,respectively.We determined the expression levels of seven out of eight miRNAs by stem-loop qPCR analysis.We also predicted the target genes of all differentially expressed miRNAs and identified the expression of some genes.Gene Ontology analyses indicated that the target genes were mainly involved in stimulus response and cellular and metabolic processes.Finally,we confirmed roles of two miRNAs in apple response to mannitol.Our results reveal candidate miRNAs and their associated mRNAs that could be targeted for improving drought tolerance in Malus species,thus providing a foundation for understanding the molecular networks involved in the response of apple trees to drought stress.

Research Progress on Rapid Breeding Technology of Anoectochilus roxburghii Seedlings

As a traditional precious Chinese herbal medicine,Anoectochilus roxburghii has the cooling and detoxifying effects,and can nourish yin to reduce pathogenic fire,and has anti-inflammatory and analgesic effects. In this paper,we summarized the research progress in detail about the biological characteristics,resource distribution,composition,medicinal value and rapid seedling breeding technology concerning the rare Chinese herbal medicine A. roxburghii,in order to provide a reference for the in-depth study and rational development and utilization of A.roxburghii.

Evaluation and application of an efficient plant DNA extraction protocol for laboratory and field testing

Nucleic acids in plant tissue lysates can be captured quickly by a cellulose filter paper and prepared for amplification after a quick purification.In this study,a published filter paper strip method was modified by sticking the filter paper on a polyvinyl chloride resin(PVC)sheet.This modified method is named EZ-D,for EASY DNA extraction.Compared with the original cetyl trimethylammonium bromide(CTAB)method,DNA extracted by EZ-D is more efficient in polymerase chain reaction(PCR)amplification due to the more stable performance of the EZ-D stick.The EZ-D method is also faster,easier,and cheaper.PCR analyses showed that DNA extracted from several types of plant tissues by EZ-D was appropriate for specific identification of biological samples.A regular PCR reaction can detect the EZ-D-extracted DNA template at concentration as low as 0.1 ng/μL.Evaluation of the EZ-D showed that DNA extracts could be successfully amplified by PCR reaction for DNA fragments up to 3000 bp in length and up to 80%in GC content.EZ-D was successfully used for DNA extraction from a variety of plant species and plant tissues.Moreover,when EZ-D was combined with the loop-mediated isothermal amplification(LAMP)method,DNA identification of biological samples could be achieved without the need for specialized equipment.As an optimized DNA purification method,EZ-D shows great advantages in application and can be used widely in laboratories where equipment is limited and rapid results are required.

Roles of endophytic fungi in medicinal plant abiotic stress response and TCM quality development

Medicinal plants,as medicinal materials and important drug components,have been used in traditional and folk medicine for ages.However,being sessile organisms,they are seriously affected by extreme environmental conditions and abiotic stresses such as salt,heavy metal,temperature,and water stresses.Medicinal plants usually produce specific secondary metabolites to survive such stresses,and these metabolites can often be used for treating human diseases.Recently,medicinal plants have been found to partner with endophytic fungi to form a long-term,stable,and win-win symbiotic relationship.Endophytic fungi can promote secondary metabolite accumulation in medicinal plants.The close relationship can improve host plant resistance to the abiotic stresses of soil salinity,drought,and extreme temperatures.Their symbiosis also sheds light on plant growth and active compound production.Here,we show that endophytic fungi can improve the host medicinal plant resistance to abiotic stress by regulating active compounds,reducing oxidative stress,and regulating the cell ion balance.We also identify the deficiencies and burning issues of available studies and present promising research topics for the future.This review provides guidance for endophytic fungi research to improve the ability of medicinal plants to resist abiotic stress.It also suggests ideas and methods for active compound accumulation in medicinal plants and medicinal material development during the response to abiotic stress.