Effect of Jasmonic Acid on Lateral Root Formation in Rice Seedling

实验材料为水稻 (OryzasativaL .)栽培品种“IR8”(国际水稻所 8号 )及其少侧根突变体MT10。将 2d水稻幼苗种子根全部浸入 0 .0 16～ 5 0 μmol/L茉莉酸 (JA)溶液处理 2d ,结果表明JA显著抑制种子根的伸长 ,其抑制程度与JA浓度成正比。不高于 2 μmol/L的JA显著促进侧根的发生 ,每cm的侧根数目随浓度的增加而增加 ,最多可增加到原来的 16 8% (“IR8”)和 2 85 % (MT10 )。 10 μmol/L的JA仍促进处理过程中和处理后生成根区段的侧根数目的增加 ,但明显抑制处理前生成根区段侧根的发生 。

Effects of in vitro subculture on the physiological characteristics of adventitious root formation in microshoots of Castanea mollissima cv.'yanshanhong'

Microshoots of Castanea mollissima cv.＇yanshanhong＇ in vitro acquired an enhanced rooting capability with increasing numbers of subculture.In this study,we investigated the effect of successive subculture on adventitious root formation in vitro by the determination of the endogenous hormone level and the enzyme activity.The levels of indoleacetic acid（IAA）,abscisic acid（ABA）,cytokinins（CTK） and gibberellic acid（GA3） were determined by high performance liquid chromatography（HPLC）,and the activities of indoleacetic acid oxidase（IAAO）,peroxidase oxidase（POD）,and polyphenol oxidase（PPO） were measured by ultraviolet-spectrophotometer assay after the induction of rooting at 2nd,4th,6th and 8th subculture.The relationships between physiological characteristics and subculture numbers or rooting rate were as follows：The levels of endogenous IAA in microshoots gradually increased,and endogenous levels of ABA,CTK and GA3 in microshoots decreased slightly after serial subcultures.The level of IAA was highly correlated with subculture numbers and rooting rates.The ratios of IAA/ABA and IAA/CTK both acutely raised with increasing rooting rate during successive subcultures and had high correlations with rooting rate.The activity of IAAO and POD are significantly negatively related with subculture numbers,and the activity of PPO increased after subcultures.

Characterization of expressed sequence tags obtained by SSH during root formation in Larix cuttings

SSH was used to analyze gene transactivation during root formation of Larix cuttings. Two subtractive cDNA libraries were constructed from clone 31-6 as tester or driver and clone 15-4 as driver or tester. The SSH PCR products from the libraries were cloned into a pGEM-T easy vector and after PCR and dot blot analysis, positive clones were selected, sequenced and compared to the database in GenBank with BLASTX. The results of a sequence assembly in two libraries show that 521 UniEST （expressed sequence tag） were obtained. These 521 UniEST belong to metabolism, signal pathways, transport, resistance, developmental processes, local- ization, unknown proteins and ＂no hits found＂. All of these suggest that subtractive cDNA libraries during root formation of Larix cuttings were constructed successfully.

Bone morphogenetic protein-2 gene controls tooth root development in coordination with formation of the periodontium

Formation of the periodontium begins following onset of tooth-root formation in a coordinated manner after birth. Dental follicle progenitor cells are thought to form the cementum, alveolar bone and Sharpey＇s fibers of the periodontal ligament （PDL）. However, little is known about the regulatory morphogens that control differentiation and function of these progenitor cells, as well as the progenitor cells involved in crown and root formation. We investigated the role of bone morphogenetic protein-2 （Bmp2） in these processes by the conditional removal of the Bmp2 gene using the Sp7-Cre-EGFP mouse model. Sp7-Cre-EGFP first becomes active at E18 in the first molar, with robust Cre activity at postnatal day 0 （PO）, followed by Cre activity in the second molar, which occurs after P0. There is robust Cre activity in the periodontium and third molars by 2 weeks of age. When the Bmp2gene is removed from Sp7＋ （Osterix＋） cells, major defects are noted in root, cellular cementum and periodontium formation. First, there are major cell autonomous defects in root-odontoblast terminal differentiation. Second, there are major alterations in formation of the PDLs and cellular cementum, correlated with decreased nuclear factor IC （Nfic）, periostin and α-SMA＋ cells. Third, there is a failure to produce vascular endothelial growth factor A （VEGF-A） in the periodontium and the pulp leading to decreased formation of the microvascular and associated candidate stem cells in the Bmp2-cKOsp7-cre＇EGFe. Fourth, ameloblast function and enamel formation are indirectly altered in the Bmp2-cKOsp7-cre＇EGFe. These data demonstrate that the Bmp2 gene has complex roles in postnatal tooth development and periodontium formation.

A Histone H3 Lysine-27 Methyltransferase Complex Represses Lateral Root Formation in Arabidopsis thaliana

Root branching or lateral root formation is crucial to maximize a root system acquiring nutrients and water from soil. A lateral root （LR） arises from asymmetric cell division of founder cells （FCs） in a pre-branch site of the primary root, and FC establishment is essential for lateral root formation. FCs are known to be specified from xylem pole pericycle cells, but the molecular genetic mechanisms underlying FC establishment are unclear. Here, we report that, in Arabidopsis thaliana, a PRC2 （for Polycomb repressive complex 2） histone H3 lysine-27 （H3K27） methyltransferase complex, functions to inhibit FC establishment during LR initiation. We found that functional loss of the PRC2 subunits EMF2 （for EMBRYONIC FLOWER 2） or CLF （for CURLY LEAF） leads to a great increase in the number of LRs formed in the primary root. The CLF H3K27 methyltransferase binds to chromatin of the auxin efflux carrier gene PIN FORMED 1 （PIN1）, deposits the repres- sive mark H3K27me3 to repress its expression, and functions to down-regulate auxin maxima in root tissues and inhibit FC establishment. Our findings collectively suggest that EMF2-CLF PRC2 acts to down-regulate root auxin maxima and show that this complex represses LR formation in Arabidopsis.

Auxin induces lateral root formation in Bupleurum: A heme oxygenase dependent approach

Objective: The content of saikosaponins in genus Bupleurum is increased with numbers of lateral root, but the genetic mechanisms are largely unknown. This study aims to identify the heme oxygenase(HO) gene family members of B. chinense and B. scorzonerifolium, and assess their role in the root development in Bupleurum.Methods: The gene sequences of HO family were selected from iso-seq full-length transcriptome data of B. chinense and B. scorzonerifolium, and were analyzed in physicochemical properties, conserved domains,motifs and phylogenetic relationship. In addition, the expression patterns of HO gene in different parts of roots were compared via transcriptome sequencing and qRT-PCR in the two species.Results: Five Bupleurum HO genes(BcHO1-BcHO5) belonging to the HO1 subfamily were identified from the transcriptome data, whereas the HO_(2) subfamily member was not identified. The expression levels of BcHO1 and BcHO_(2) were significantly higher than those of other three HO members in the transcriptome analysis. In addition, the expression profile of BcHO1 showed consistency with lateral root development in B. chinense and B. scorzonerifolium.Conclusion: Hos might participate in the auxin-induced morphogenesis of lateral roots. The yield of saikosaponin may be improved by manipulating expression of these genes.

Identification of the nitrogen-fixing Pseudomonas stutzeri major flagellar gene regulator FleQ and its role in biofilm formation and root colonization

Flagellar biosynthesis and motility are subject to a four-tiered transcriptional regulatory circuit in Pseudomonas,and the master regulator FleQ appears to be the highest-level regulator in this hierarchical regulatory cascade.Pseudomonas stutzeri A1501 is motile by a polar flagellum;however,the motility and regulatory mechanisms involved in this process are unknown.Here,we searched the A1501 genome for flagella and motility genes and found that approximately 50 genes,which were distributed in three non-contiguous chromosomal regions,contribute to the formation,regulation and function of the flagella.The non-polar mutation of fleQ impaired flagellar biosynthesis,motility and root colonization but enhanced biofilm formation.FleQ positively regulates the expression of flagellar class Ⅱ-Ⅳ genes,suggesting a regulatory cascade that is coordinated similar to that of the well-known P.aeruginosa.Based on our results,we propose that flagellar genes in P.stutzeri A1501 are regulated in a cascade regulated by FleQ and that flagellum-driven motility properties may be necessary for competitive rhizosphere colonization.

Application of biostimulants for vegetative propagation of endangered Abies gracilis

Abies gracilis Kom.(Pinaceae)is one of the rarest and endangered conifers in the Russian flora,which must be cultivated ex situ to ensure its survival.Cuttings of A.gracilis do not take root without biostimulants.We used a selection of biostimulants,concentrations,and conditions of their use to significantly increase Abies gracilis rooting,and to accelerate the production of planting material,and to reduce rooting time to one season.We tested 4 rooting systems:IBA,IBA with glucose and glycine,and original biostimulants(S-try and S-5).The original S-5 biostimulating system had the most balanced ratio of components.The number of rooted samples increased 2.7 times and the length of roots increased 1.8 time when using S-5 as compared to IBA.S-try and S-5-original biostimulant systems were synthesized and collected in 2011 and 2014,respectively,and were tested in St.Petersburg Forest Technical University.

High Efficiency of Propagation for Sagittaria sagittifolia Using a Temporary Immersion Bioreactor System

Although several studies have reported on the propagation of the Sagittaria sagittifolia to date, none of these methods have efficiently achieved the mass production of these plants. The present study aimed to investigate the propagation and growth of S. sagittifolia using a temporary immersion bioreactor system （TIBS） compared with conventional semi-solid and liquid culture. The effect of different immersion frequencies and immersion times together with supplementation of various plant growth regulators to the Murashige and Skoog （MS） medium was evaluated on shoot proliferation and plant growth. The results showed that the higher immersion frequency （every 6 h） and shorter immersion time （3 min and 10 rain） in medium containing 4 mg/L BA and 0.1 mg/L NAA produced the highest multiplication rate （23）, which are significantly higher than conventional semi-solid （3.6） and liquid （4.5） method, and the best plant growth parameter. While, the lower immersion frequency and longer immersion time （30 rain every 12 h and 60 min every 24 h） induced vitrification and pollution rate in shoot tips 16.6% and 19%, 42% and 37%, respectively. There is distinct decrease in pollution rate （8.3%） in TIBS （10 min every 6 h） compared with the conventional semi-solid and liquid cultures. Medium containing 4 mg/L BA and 0.5 mg/L NAA using 10 min immersion every 6 h showed satisfaction at the rooting stage, with high shoot proliferation rate （21.6）, 100% rooting and 94% plant survival. Therefore, applying TIBS in S. sagittifolia is an efficient method for scaling up the production of plantlets with high quality seedlings.

Transcriptional mechanisms regulating gene expression and determining cell fates in plant development

Transcriptional regulatory mechanisms that control transcriptional regulators, target genes, and their interactions provide new insights into general development processes throughout the life cycle of the plant. Although different molecular mechanisms that regulate plant growth and development have been identified, detailed transcriptional mechanisms that control gene expression, modulate developmental programmes, and determine cell fates in plant development are not fully understood. To increase our understanding on transcriptional mechanisms regulating diverse processes in plant development, we have reviewed the regulation of transcription during the process of development including transcriptional mechanisms regulating root, stem, leaf, flower, seed, embryo, endosperm, ovule, fruit, and chloroplast development. We have summarized the interaction, expression, transport, signaling events of transcriptional regulators and their targets in a number of model plants and highlighted the involvement of hormones and microRNAs in plant development. Understanding the precise transcriptional mechanisms regulating gene expression in plant development will be valuable for plant molecular breeding.

Factors involved in the success of Castanea henryi stem cuttings in different cutting mediums and cutting selection periods

Chinquapin(Castanea henryi) is a dual-purpose tree species in China valued for as a source of timber and starch.We investigated the effect of four cutting mediums(pure vermiculite;peat:river sand at 3:1 v/v;peat:krasnozem at 1:1 v/v;and pure krasnozem) and three stem cutting periods(March,May,and July) on rooting performance of C.henryi cuttings.Different cutting periods and cutting mediums greatly influenced the rooting rate of C.henryi,ranging from 3.35 to 77.31%.Principal component analysis indicated that the best combination of cutting period and cutting medium was semi-hardwood cuttings(May cuttings)+krasnozem.Histological evidence indicated that adventitious root initials were present by week 5-6,and that the site of root primordia initiation was observed in the vascular cambium.Stem anatomical structures observed at different periods indicated that a xylem/radius ratio of29.90-37.42% and a fractured phloem fiber ring are indicative of rooting success.The relational model between rooting index and medium properties indicated that nutrient content and porosity significantly influenced callus production.However,pH strongly affected C.henryi root formation,with the Pearson correlation coefficients for May and July cuttings of-0.856 and-0.947,respectively.Our protocol is helpful to achieve mass clone propagation of improved C.henryi genotypes,thus overcoming a common hurdle in chinquapin breeding programs.