RcSPL1-RcTAF15b regulates the flowering time of rose (Rosa chinensis)

Rose(Rosa chinensis),which is an economically valuable floral species worldwide,has three types,namely once-flowering(OF),occasional or re-blooming(OR),and recurrent or continuous flowering(CF).However,the mechanism underlying the effect of the age pathway on the duration of the CF or OF juvenile phase is largely unknown.In this study,we observed that the RcSPL1 transcript levels were substantially upregulated during the floral development period in CF and OF plants.Additionally,accumulation of RcSPL1 protein was controlled by rch-miR156.The ectopic expression of RcSPL1 in Arabidopsis thaliana accelerated the vegetative phase transition and flowering.Furthermore,the transient overexpression of RcSPL1 in rose plants accelerated flowering,whereas silencing of RcSPL1 had the opposite phenotype.Accordingly,the transcription levels of floral meristem identity genes(APETALA1,FRUITFULL,and LEAFY)were significantly affected by the changes in RcSPL1 expression.RcTAF15b protein,which is an autonomous pathway protein,was revealed to interact with RcSPL1.The silencing and overexpression of RcTAF15b in rose plants led to delayed and accelerated flowering,respectively.Collectively,the study findings imply that RcSPL1–RcTAF15b modulates the flowering time of rose plants.

Microbe-induced gene silencing explores interspecies RNAi and opens up possibilities of crop protection

In most eukaryotes, small RNA(sRNA)-mediated RNA silencing(or RNA interference, RNAi) is an evolutionarily conserved mechanism that regulates gene expression in a sequence-specific manner.Generally, s RNAs are produced by the RNase III enzymes Dicers and then incorporated into Argonaute(AGO) proteins to regulate gene expression by mRNA degradation.

Emaravirus属新病毒:中国枣树花叶伴随病毒全基因组测序

[目的]2016年以来,新疆阿克苏等地区出现了一种新的枣树病害,严重威胁当地及周边红枣产业。本研究旨在鉴定引起此次病害的病原,探究病原体的传播方式,为生物防治策略的开发提供研究基础。[方法]对发病植株进行小RNA测序以鉴定病原体;对新鉴定的病毒,通过RNAseq和反转录PCR获取病毒全序列;体外表达重组的病毒结构蛋白并制备特异性抗体,通过Western斑点杂交法在发病植株中确证病毒蛋白;收集发病区域的媒介昆虫,通过反转录PCR在昆虫体内检测病毒的基因组,鉴定可能的传毒介体。[结果]本研究鉴定一种新的欧洲山梣环斑病毒属病毒为新疆新发枣树病害可能的病原体,命名为中国枣树花叶伴随病毒(Chinese date mosaic-associated virus,CDMaV)。CDMaV是一种多分段单链RNA病毒,基因组由5条负义RNA组成;RNA1-RNA5大小分别为7160、2224、1230、1493、971 nt,每条基因组RNA的互补链包含一个开放阅读框,共编码5个蛋白,依次为依赖RNA的RNA聚合酶、包膜糖蛋白、核衣壳蛋白和两个未知功能蛋白。在枣树寄生虫枣瘿螨体内扩增到病毒序列,表明该病毒可能以枣瘿螨为介体在枣树间进行传播。[结论]本研究为新疆新发枣树病害鉴定了相关病原体CDMaV,完成CDMaV全基因组测序,并鉴定枣瘿螨为可能的传毒介体。鉴定病原体和传播介体是建立病害防治方法的必要基础。

Purification and Characterization of a New Ribosome Inactivating Protein from Cinchonaglycoside C-treated Tobacco Leaves

A new ribosome-inactivating protein （RIP） with a molecular weight of 31 kDa induced by Cinchonaglycoside C （1） designated CIP31, was isolated from tobacco leaves. Analysis of this protein sequence indicated that it belongs to the RIP family and it was distinct from the other plant RIPs reported previously at its N-terminal amino acid sequence. CIP31 can directly impair synthesis of coat protein （CP） of tobacco mosaic virus （TMV）, which resulted in inhibition of TMV long distance movement and multiplication in tobacco plants at concentrations of ng/mL. Furthermore, no toxicity was shown to the growth and fertility of the plants. CIP31 was synthesized only in the presence of Cinchonaglycoside C （1） and was independent of the salicylic acid （SA） signal pathway. We provided evidence for the SA-independent biological induction of resistance.

Interkingdom signaling in plant-microbe interactions

The widespread communications between prokaryotes and eukaryotes via signaling molecules are believed to affect gene expression in both partners.During the communication process,the contacted organisms produce and release small molecules that establish communication channels between two kingdoms—this procedure is known as interkingdom signaling.Interkingdom communications are widespread between pathogenic or beneficial bacteria and their host plants,with diversified outcomes depending on the specific chemical-triggered signaling pathways.Deciphering the signals or language of this interkingdom communication and uncovering the underlying mechanisms are major current challenges in this field.It is evident that diverse signaling molecules can be produced or derived from bacteria and plants,and researchers have sought to identify these signals and explore the mechanisms of the signaling pathways.The results of such studies will lead to the development of strategies to improve plant disease resistance through controlling interkingdom signals,rather than directly killing the pathogenic bacteria.Also,the identification of signals produced by beneficial bacteria will be useful for agricultural applications.In this review,we summarize the recent progress of cross-kingdom interactions between plant and bacteria,and how LuxR-family transcription factors in plant associated bacterial quorum sensing system are involved in the interkingdom signaling.

Small G Protein as a Novel Component of the Rice Bmssinosteroid Signal Transduction

Brassinosteroids （BRs） are a class of steroid hormones that are essential for plant growth and development. The BR signal transduction pathway in the dicot model plantArabidopsis is well established, but the components connecting the BR signaling steps in rice have not been fully explored. For example, how the BR signaling is fine-tuned in rice, especially at the BR receptor level, is largely unknown. Here we show that OsPRA2, a rice small G protein, plays a repressive role in the BR signaling pathway. Lamina inclination, coleoptile elongation, and root inhibition assays indicated that rice plants with suppressed expression of OsPRA2 were more sensitive to exogenously applied brassinolide than the wild-type plants. Conversety, rice overexpressing OsPRA2 was less sensitive to exogenous brassinolide. Further study uncovered that OsPRA2 inhibited the dephosphorylation of, and thus inactivated the transcription factor BRASSINAZOLE- RESISTANT 1 （OsBZR1）. More importantly, OsPRA2 was found to co-localize with and directly bind to rice BR receptor BRASSlNOSTEROID-INSENSITIVE 1 （OsBRI1） at the plasma membrane. Additionally, the in vitro assays showed that OsPRA2 inhibits its autophosphorylation. This OsPRA2-OsBRI1 interaction led to the dissociation of OsBRI1 from its co-receptor OsBAK1, and abolished OsBRIl-mediated phosphorylation of OsBAK1. Together, these results reveal a possible working mechanism of OsPRA2 as a novel negative regu- lator on OsBRI1 and OsBZR1 and extend the knowledge about the regulatory mechanism of rice BR signaling.

SRWD1, a novel target gene of DELLA and WRKY proteins, participates in the development and immune response of rice (Oryza sativa L.)

SRWD1, a member of the WD40 protein subfamily, is induced by salt stress in rice and its homolog in barley can bind to GAMYB, implying that SRWD1 might be involved in plant defense against environmental stress and gibberellic acid(GA) signalings. In this study, we focused on the biological functions and regulation mechanisms of SRWD1 in rice. The results showed that SRWD1 expression was repressed by GA and induced by abscisic acid(ABA). Two WRKY-family transcription factors, Os WRKY45 and Os WRKY72, were found to regulate SRWD1 expression by directly binding to the W-box region in its promoter. Transient co-expression and yeast two-hybrid analyses showed that a DELLA protein strengthened the activation of Os WRKY45 and partly relieved the suppression of Os WRKY72 by binding to them.Interestingly, both SRWD1-overexpressing transgenic plants and SRWD1-knockout mutants showed dwarf phenotypes and resistance to Xanthomonas oryzae.

Designing specific bacterial 16S primers to sequence and quantitate plant endo-bacteriome

Plant endophytic bacteria colonize the internal tissues of plants and interact with plants closely.The past two decades have witnessed the increasing application of next-generation 16S r RNA gene sequencing in the investigation of bacterial communities.However,deciphering plant endo-bacterial communities by this method is difficult because of the co-amplification of massive plant organellar DNAs with bacterial 16S.Here,we designed polymerase chain reaction(PCR) primer sets,including799F/1107R,322F/796R,and 322F-Dr/796Rs(primer pair 322F/796R with a penultimate-base substitution in 322F),that can specifically amplify bacterial 16S from plant total DNAs.We computationally and experimentally evaluated the specificity,coverage,and accuracy of the newly designed primer sets.Both 799F/1107R and 322F-Dr/796Rs produced plant DNA-free 16S amplicon libraries or reduced plant DNA contamination to lower than 5% for the plant materials with extremely-low-abundance bacterial communities.The primer set 322F-A/796R was used through absolute quantitative PCR to quantitate the population size of rice leaf or root endo-bacteriome,which revealed 10^(6)–10^(7) and 10^(9)–10^(10) bacteria per gram fresh weight,respectively.These 16S primer sets and amplification methods enable the simple and inexpensive next-generation sequencing and quantification of plant endo-bacteriome,which will significantly advance studies on the plant-related microbiome.

Manipulation of biotic signaling:a new theory for smarter pest control

Modem agricultural bio-technologies have significantly increased the efficiency and quality of crop production and contributed to the improvement of people＇s life in the world. Widespread utilization of fertilizers, herbicides, fun- gicides, pesticides, antibiotics, and plant growth regulators has been instrumental in securing crop yields to feed over seven billions of human beings in the earth. However, dur- ing the recent half century, extensive uses of pesticides and other chemicals, which traditionally target the essential physiological pathways of pathogenic microbes and pests, have proverbial, negative impacts on the environmental and human health. Therefore, the urgent demands for sustaina- ble agriculture rely on a better understanding of interactions between pants and other organisms and the underpinning molecular metabolisms.

Heterosis in root microbiota inhibits growth of soil-borne fungal pathogens in hybrid rice

In nature,plants are colonized by various microbes that play essential roles in their growth and health.Heterosis is a natural genetic phenomenon whereby first-generation hybrids exhibit superior phenotypic performance relative to their parents.It remains unclear whether this concept can be extended to the“hybridization”of microbiota from two parents in their descendants and what benefits the hybrid microbiota might convey.Here,we investigated the structure and function of the root microbiota from three hybrid rice varieties and their parents through amplicon sequencing analysis of bacterial 16S ribosomal DNA(rDNA)and fungal internal transcribed spacer(ITS)regions.We show that the bacterial and fungal root microbiota of the varieties are distinct from those of their parental lines and exhibit potential heterosis features in diversity and composition.Moreover,the root bacterial microbiota of hybrid variety LYP9 protects rice against soil-borne fungal pathogens.Systematic analysis of the protective capabilities of individual strains from a 30-member bacterial synthetic community derived from LYP9 roots indicated that community members have additive protective roles.Global transcription profiling analyses suggested that LYP9 root bacterial microbiota activate rice reactive oxygen species production and cell wall biogenesis,contributing to heterosis for protection.In addition,we demonstrate that the protection conferred by the LYP9 root microbiota is transferable to neighboring plants,potentially explaining the observed hybrid-mediated superior effects of mixed planting.Our findings suggest that some hybrids exhibit heterosis in their microbiota composition that promotes plant health,highlighting the potential for microbiota heterosis in breeding hybrid crops.

The Rice＇NUTRITION RESPONSE AND ROOT GROWTH＇ （NRR） Gene Regulates Heading Date

Dear Editor, As one of the most important developmental traits, flow-ering time has been extensively investigated in the long-day plant Arabidopsis. Multiple factors are involved, including photoperiod and/or temperature （Amasino, 2010）. Flowering locus T （FT） is known to be an important integrator of dif-ferent flowering pathways （Taoka et al., 2011）. Genes of the CONSTANS （CO） family also play key roles in regulating flow-ering time. The CO protein consists of a zinc finger and a CCT domain shared by a group of plant-specific transcription fac-tors that regulate photoperiodic flowering response and cir-cadian rhythms in Arabidopsis.

RoTFL1c of Rosa multiflora has a dual-function in suppressing reproductive growth and promoting vegetative growth of Arabidopsis

Dear Editor, TFL1homologues play a key role in the flowering habit of roses.To analyze the function of the newly isolated TFL1 gene of Rosa multiflora(Chen et al.,2013),named RoTFLlc,we performed overexpression analyses in Arabidopsis thaliana.When compared with empty vector control and wild type Arabidopsis plants,RoTFLlc overexpressing transgenic plants exhibited strong phenotypes such as a clustered habit,an increased number of rosette leaves, late flowering or failure to flower.