Perennial Woody Plants Research Articles

A comprehensive analysis of the floral transition in ma bamboo (Dendrocalamus latiflorus) reveals the roles of DlFTs involved in flowering.

Bamboo has a unique flowering characteristics of long and unpredictable vegetative period, which differs from annual herbs and perennial woody plants. In order to understand the molecular regulatory mechanism of bamboo flowering, a comprehensive study was conducted in ma bamboo (Dendrocalamus latiflorus Munro), including morphological, physiological and transcriptiome analyses. Differentially expressed genes related to the flowering pathway were identified by comparative transcriptome analysis. DlFT1, a homologous gene of FT/Hd3a, was significantly upregulated in flowering bamboo. Direct differentiation of spikelets from calli occurred and the downstream gene AP1 was upregulated in the transgenic bamboo overexpressing DlFT1. Transgenic rice overexpressing DlFT1 showed a strong early flowering phenotype. DlFT1 and DlTFL1 could interact with DlFD, and DlTFL1 delayed flowering. It is presumed that DlTFL1 plays an antagonistic role with DlFT1 in ma bamboo. In addition, the expression of DlFT1 was regulated by DlCO1, indicating that a CO-FT regulatory module might exist in ma bamboo. These results suggest that DlFT1 is a florigen candidate gene with conservative function in promoting flowering. Interestingly, the results have shown for the first time that DlFT2 can specifically interact with E3 ubiquitin ligase WAV3, while DlFT3 transcripts are mainly nonsense splicing. These findings provide better understanding of the roles of the florigen gene in bamboo and lay a theoretical basis for regulating bamboo flowering in the future.

Transposon insertions regulate genome‐wide allele‐specific expression and underpin flower colour variations in apple (Malus spp.)

SummaryAllele‐specific expression (ASE) can lead to phenotypic diversity and evolution. However, the mechanisms regulating ASE are not well understood, particularly in woody perennial plants. In this study, we investigated ASE genes in the apple cultivar ‘Royal Gala’ (RG). A high quality chromosome‐level genome was assembled using a homozygous tetra‐haploid RG plant, derived from anther cultures. Using RNA‐sequencing (RNA‐seq) data from RG flower and fruit tissues, we identified 2091 ASE genes. Compared with the haploid genome of ‘Golden Delicious’ (GD), a parent of RG, we distinguished the genomic sequences between the two alleles of 817 ASE genes, and further identified allele‐specific presence of a transposable element (TE) in the upstream region of 354 ASE genes. These included MYB110a that encodes a transcription factor regulating anthocyanin biosynthesis. Interestingly, another ASE gene, MYB10 also showed an allele‐specific TE insertion and was identified using genome data of other apple cultivars. The presence of the TE insertion in both MYB genes was positively associated with ASE and anthocyanin accumulation in apple petals through analysis of 231 apple accessions, and thus underpins apple flower colour evolution. Our study demonstrated the importance of TEs in regulating ASE on a genome‐wide scale and presents a novel method for rapid identification of ASE genes and their regulatory elements in plants.

A chromosome-level genome sequence assembly of the red raspberry (Rubus idaeus L.).

Rubus idaeus L. (red raspberry), is a perennial woody plant species of the Rosaceae family that is widely cultivated in the temperate regions of world and is thus an economically important soft fruit species. It is prized for its flavour and aroma, as well as a high content of healthful compounds such as vitamins and antioxidants. Breeding programs exist globally for red raspberry, but variety development is a long and challenging process. Genomic and molecular tools for red raspberry are valuable resources for breeding. Here, a chromosome-length genome sequence assembly and related gene predictions for the red raspberry cultivar ‘Anitra’ are presented, comprising PacBio long read sequencing scaffolded using Hi-C sequence data. The assembled genome sequence totalled 291.7 Mbp, with 247.5 Mbp (84.8%) incorporated into seven sequencing scaffolds with an average length of 35.4 Mbp. A total of 39,448 protein-coding genes were predicted, 75% of which were functionally annotated. The seven chromosome scaffolds were anchored to a previously published genetic linkage map with a high degree of synteny and comparisons to genomes of closely related species within the Rosoideae revealed chromosome-scale rearrangements that have occurred over relatively short evolutionary periods. A chromosome-level genomic sequence of R. idaeus will be a valuable resource for the knowledge of its genome structure and function in red raspberry and will be a useful and important resource for researchers and plant breeders.

Comprehensive Analyses of Four PtoNF-YC Genes from Populus tomentosa and Impacts on Flowering Timing.

Flowering is an important link in the life process of angiosperms, and it is also an important sign of the transformation of plants from vegetative to reproductive growth. Although the flowering regulation network of Arabidopsis is well-understood, there has been little research on the molecular mechanisms of perennial woody plant flower development regulation. Populus tomentosa is a unique Chinese poplar species with fast growth, strong ecological adaptability, and a long lifecycle. However, it has a long juvenile phase, which seriously affects its breeding process. Nuclear factor-Y (NF-Y) is an important type of transcription factor involved in the regulation of plant flowering. However, there are few reports on PtoNF-Y gene flowering regulation, and the members of the PtNF-YC subfamily are unknown. In this study, four key genes were cloned and analyzed for sequence characteristics, gene structure, genetic evolution, expression patterns, and subcellular localization. The plant expression vector was further constructed, and transgenic Arabidopsis and P. tomentosa plants were obtained through genetic transformation and a series of molecular tests. The flowering time and other growth characteristics were analyzed. Finally, the expression level of flowering genes was detected by quantitative PCR, the interaction between PtoNF-YC and PtoCOL proteins was measured using the yeast two-hybrid system to further explain the flowering regulation mechanism, and the molecular mechanisms by which PtNF-YC6 and PtNF-YC8 regulate poplar flowering were discussed. These results lay the foundation for elucidating the molecular regulation mechanism of PtoNF-YC in flowering and furthering the molecular design and breeding of poplar, while providing a reference for other flowering woody plants.

A High-Quality Reference Genome Sequence and Genetic Transformation System of Aralia elata.

Aralia elata is a perennial woody plant of the genus Aralia in the family Araliaceae. It is rich in saponins and therefore has a wide range of pharmacological effects. Here, we report a high-quality reference genome of A. elata, with a genome size of 1.21 Gb and a contig N50 of 51.34 Mb, produced by PacBio HiFi sequencing technology. This is the first genome assembly for the genus Aralia. Through genome evolutionary analysis, we explored the phylogeny and whole genome duplication (WGD) events in the A. elata genome. The results indicated that a recent WGD event occurred in the A. elata genome. Estimation of the divergence times indicated that the WGD may be shared by Araliaceae. By analyzing the genome sequence of A. elata and combining the transcriptome data from three tissues, we discovered important genes related to triterpene saponins biosynthesis. Furthermore, based on the embryonic callus induction system of A. elata established in our laboratory, we set up the genetic transformation system of this plant. The genomic resources and genetic transformation system obtained in this study provide insights into A. elata and lays the foundation for further exploration of the A. elata regulatory mechanism.

The Genetic Basis of Phosphorus Utilization Efficiency in Plants Provide New Insight into Woody Perennial Plants Improvement.

Soil nutrient restrictions are the main environmental conditions limiting plant growth, development, yield, and quality. Phosphorus (P), an essential macronutrient, is one of the most significant factors that vastly restrains the growth and development of plants. Although the total P is rich in soil, its bio-available concentration is still unable to meet the requirements of plants. To maintain P homeostasis, plants have developed lots of intricate responsive and acclimatory mechanisms at different levels, which contribute to administering the acquisition of inorganic phosphate (Pi), translocation, remobilization, and recycling of Pi. In recent years, significant advances have been made in the exploration of the utilization of P in annual plants, while the research progress in woody perennial plants is still vague. In the meanwhile, compared to annual plants, relevant reviews about P utilization in woody perennial plants are scarce. Therefore, based on the importance of P in the growth and development of plants, we briefly reviewed the latest advances on the genetic and molecular mechanisms of plants to uphold P homeostasis, P sensing, and signaling, ion transporting and metabolic regulation, and proposed the possible sustainable management strategies to fasten the P cycle in modern agriculture and new directions for future studies.

Plant organ and sampling time point determine the taxonomic structure of microbial communities associated to apple plants in the orchard environment

Plant-associated microbial communities interact with their host and are important components of the biodiversity of natural and agro-ecosystems. Scarce knowledge is available on the establishment of plant microbiota in perennial woody plants. In this work the variability in bacterial and fungal communities in aboveground organs was analysed in leaves, bark, flowers and fruits on three apple cultivars (Gala, Fuji and Golden), in order to understand changes of the microbiota community structure from orchard planting to the first year of fruit production. Our results indicate that Proteobacteria, Bacterioidetes, Actinobacteria and Firmiculites were the dominant bacterial phyla across all samples. The majority of fungal sequences were assigned to Ascomycota and Basidiomycota. The bacterial genera Pseudomonas and Sphingomonas, and the fungal genera Aureobasidium and Filobasidium, represented a major component of the aboveground microbiota. Different parts of the apple plant harboured a specific microbiota and the effect of plant organ on the bacterial and fungal taxonomic structure exceeded the influence of sampling time and plant genotype. This work highlights the specificity of the microbiota associated with aboveground apple organs, changes of the microbiota composition during the plant development from orchard planting to the first year of fruit production, and the negligible effects of apple cultivar.

Cytology, transcriptomics, and mass spectrometry imaging reveal changes in late-maturation elm (Ulmus pumila) seeds

During seed maturation, the seed deposits storage compounds (starches, oils, and proteins), synthesizes defense compounds, produces a seed coat, initiates embryo dormancy, and becomes desiccated. During the late-maturation stage, seed storage compound contents and compositions change dramatically. Although maturation has been extensively studied in model species and crops, it remains less well characterized in woody perennial plants. In this study, we conducted morphological and cytological observations, transcriptome profiling, and chemical constituent analysis of elm (Ulmus pumila L.) seeds during the late-maturation stage. Light and electron microscopy revealed that closely packed yet discrete lipid bodies frequently surrounded the densely stained protein bodies, and the protein bodies became irregular or even partially disintegrated at the end of seed development. RNA-seq detected substantial transcriptome changes during the late-maturation stage, and pathway enrichment analysis showed that the differentially expressed genes were associated with phenylpropanoid biosynthesis, starch and sucrose metabolism, plant–pathogen interactions, and hormone signal transduction. Furthermore, we used mass spectrometry imaging to detect the relative intensity and spatial distribution of fatty acids, phospholipids, and waxes in elm seeds. Our findings provide a framework for understanding the changes in cytological features and chemical composition during the final stage of elm seed development, and a detailed reference for seed development in woody plants.

Characterization of the bark storage protein gene (JcBSP) family in the perennial woody plant Jatropha curcas and the function of JcBSP1 in Arabidopsis thaliana.

BackgroundBark storage protein (BSP) plays an important role in seasonal nitrogen cycling in perennial deciduous trees. However, there is no report on the function of BSP in the perennial woody oil plant Jatropha curcas.MethodsIn this study, we identified six members of JcBSP gene family in J. curcas genome. The patterns, seasonal changes, and responses to nitrogen treatment in gene expression of JcBSPs were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Overexpression of JcBSP1 in transgenic Arabidopsis thaliana was driven by a constitutive cauliflower mosaic virus (CaMV) 35S RNA promoter.ResultsJcBSP members were found to be expressed in various tissues, except seeds. The seasonal changes in the total protein concentration and JcBSP1 expression in the stems of J. curcas were positively correlated, as both increased in autumn and winter and decreased in spring and summer. In addition, the JcBSP1 expression in J. curcas seedlings treated with different concentrations of an NH4NO3 solution was positively correlated with the NH4NO3 concentration and application duration. Furthermore, JcBSP1 overexpression in Arabidopsis resulted in a phenotype of enlarged rosette leaves, flowers, and seeds, and significantly increased the seed weight and yield in transgenic plants.

PAs Regulate Early Somatic Embryo Development by Changing the Gene Expression Level and the Hormonal Balance in Dimocarpus longan Lour.

Polyamines (PAs) play an important regulatory role in many basic cellular processes and physiological and biochemical processes. However, there are few studies on the identification of PA biosynthesis and metabolism family members and the role of PAs in the transition of plant embryogenic calli (EC) into globular embryos (GE), especially in perennial woody plants. We identified 20 genes involved in PA biosynthesis and metabolism from the third-generation genome of longan (Dimocarpus longan Lour.). There were no significant differences between longan and other species regarding the number of members, and they had high similarity with Citrus sinensis. Light, plant hormones and a variety of stress cis-acting elements were found in these family members. The biosynthesis and metabolism of PAs in longan were mainly completed by DlADC2, DlSAMDC2, DlSAMDC3, DlSPDS1A, DlSPMS, DlCuAOB, DlCuAO3A, DlPAO2 and DlPAO4B. In addition, 0.01 mmol∙L−1 1-aminocyclopropane-1-carboxylic acid (ACC), putrescine (Put) and spermine (Spm), could promote the transformation of EC into GE, and Spm treatment had the best effect, while 0.01 mmol∙L−1 D-arginine (D-arg) treatment inhibited the process. The period between the 9th and 11th days was key for the transformation of EC into GE in longan. There were higher levels of gibberellin (GA), salicylic acid (SA) and abscisic acid (ABA) and lower levels of indole-3-acetic acid (IAA), ethylene and hydrogen peroxide (H2O2) in this key period. The expression levels in this period of DlADC2, DlODC, DlSPDS1A, DlCuAOB and DlPAO4B were upregulated, while those of DlSAMDC2 and DlSPMS were downregulated. These results showed that the exogenous ACC, D-arg and PAs could regulate the transformation of EC into GE in longan by changing the content of endogenous hormones and the expression levels of PA biosynthesis and metabolism genes. This study provided a foundation for further determining the physicochemical properties and molecular evolution characteristics of the PA biosynthesis and metabolism gene families, and explored the mechanism of PAs and ethylene for regulating the transformation of plant EC into GE.

Roles of auxin in the inhibition of shoot branching in 'Dugan' fir.

Shoot branching substantially impacts vegetative and reproductive growth as well as wood characteristics in perennial woody species by shaping the shoot system architecture. Although plant hormones have been shown to play a fundamental role in shoot branching in annual species, their corresponding actions in perennial woody plants are largely unknown, in part due to the lack of branching mutants. Here, we demonstrated the role of plant hormones in bud dormancy transition toward activation and outgrowth in woody plants by comparing the physiological and molecular changes in the apical shoot stems of 'Yangkou' 020 fir and 'Dugan' fir, two Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) clones with normal and completely abolished branching phenotypes, respectively. Our studies showed that the defect in bud outgrowth was the cause of failed shoot branching in 'Dugan' fir whereas apically derived signals acted as triggers of this ectopic bud activity. Further studies indicated that auxin played a key role in inhibiting bud outgrowth in 'Dugan' fir. During bud dormancy release, the differential auxin resistant 1/Like AUX1 (AUX1/LAX) and PIN-formed (PIN) activity resulted in an ectopic auxin/indole-3-acetic acid (IAA) accumulation in the apical shoot stem of 'Dugan' fir, which could inhibit the cell cycle in the axillary meristem by decreasing cytokinin (CK) biosynthesis but increasing abscisic acid (ABA) production and response through the signaling pathway. In contrast, during bud activation and outgrowth, the striking increase in auxin biosynthesis and PIN activity in the shoot tip of 'Dugan' fir may trigger the correlative inhibition of axillary buds by modulating the polar auxin transport stream (PATS) and connective auxin transport (CAT) in shoots, and by influencing the biosynthesis of secondary messengers, including CK, gibberellin (GA) and ABA, thereby inducing the paradormancy of axillary buds in 'Dugan' fir by apical dominance under favorable conditions. The findings of this study provide important insights into the roles of plant hormones in bud outgrowth control in perennial woody plants.

Target of rapamycin (TOR) regulates the response to low nitrogen stress via autophagy and hormone pathways in Malus hupehensis.

Target of rapamycin (TOR) is a highly conserved master regulator in eukaryotes; it regulates cell proliferation and growth by integrating different signals. However, little is known about the function of TOR in perennial woody plants. Different concentrations of AZD8055 (an inhibitor of TOR) were used in this study to investigate the role of TOR in the response to low nitrogen (N) stress in the wild apple species Malus hupehensis. Low N stress inhibited the growth of M. hupehensis plants, and 1 μM AZD alleviated this effect. Plants supplied with 1 μM AZD had higher photosynthetic capacity, which promoted the accumulation of biomass, as well as higher contents of N and anthocyanins and lower content of starch. Exogenous application of 1 μM AZD also promoted the development of the root system. Plants supplied with at least 5 μM AZD displayed early leaf senescence. RNA-seq analysis indicated that TOR altered the expression of genes related to the low N stress response, such as genes involved in photosystem, starch metabolism, autophagy, and hormone metabolism. Further analysis revealed altered autophagy in plants supplied with AZD under low N stress; the metabolism of plant hormones also changed following AZD supplementation. In sum, our findings revealed that appropriate inhibition of TOR activated autophagy and jasmonic acid signaling in M. hupehensis, which allowed plants to cope with low N stress. Severe TOR inhibition resulted in the excessive accumulation of salicylic acid, which probably led to programmed cell death in M. hupehensis.

Mobility of FLOWERING LOCUS T protein as a systemic signal in trifoliate orange and its low accumulation in grafted juvenile scions.

The long juvenile period of perennial woody plants is a major constraint in breeding programs. FLOWERING LOCUS T (FT) protein is an important mobile florigen signal that induces plant flowering. However, whether FT can be transported in woody plants to shorten the juvenile period is unknown, and its transport mechanism remains unclear. In this study, trifoliate orange FT (ToFT) and Arabidopsis FT (AtFT, which has been confirmed to be transportable in Arabidopsis) as a control were transformed into tomato and trifoliate orange, and early flowering was induced in the transgenic plants. Long-distance and two-way (upward and downward) transmission of ToFT and AtFT proteins was confirmed in both tomato and trifoliate orange using grafting and western blot analysis. However, rootstocks of transgenic trifoliate orange could not induce flowering in grafted wild-type juvenile scions because of the low accumulation of total FT protein in the grafted scions. It was further confirmed that endogenous ToFT protein was reduced in trifoliate orange, and the accumulation of the transported ToFT and AtFT proteins was lower than that in grafted juvenile tomato scions. Furthermore, the trifoliate orange FT-INTERACTING PROTEIN1 homolog (ToFTIP1) was isolated by yeast two-hybrid analysis. The FTIP1 homolog may regulate FT transport by interacting with FT in tomato and trifoliate orange. Our findings suggest that FT transport may be conserved between the tomato model and woody plants. However, in woody plants, the transported FT protein did not accumulate in significant amounts in the grafted wild-type juvenile scions and induce the scions to flower.

Lignin biosynthesis and accumulation in response to abiotic stresses in woody plants

Woody plants have to experience various abiotic stresses due to their immobility and perennial characteristics. However, woody plants have evolved a series of specific regulation pathways in physiological and molecular mechanisms to deal with adverse environments. Compared with herbaceous plants, perennial woody plants have the advantages of developed roots and hard stems, and increased secondary xylem, which can strengthen the vascular system of the plants. The lignification process involves the lignin deposition on the cell wall by oxidation and polymerization of lignin monomer, which plays an important role in abiotic stress tolerance. This review focuses on recent progress in the biosynthesis, content, and accumulation of lignin in response to various abiotic stresses in plants. The role of transcription factors is also discussed in regulating lignin biosynthesis to enhance abiotic stress tolerance <italic>via</italic> changing cell wall lignification. Although woody plants shared similar lignin biosynthesis mechanisms with herbaceous plants, the temporal and spatial expression and stress response profiles of lignin biosynthetic genes provide the basis for the differences in stress tolerance of various species. An in-depth understanding of the role of lignin in the abiotic stress tolerance of woody plants will lay the foundation for the next step in tree resistance breeding through genetic engineering.

Biolistic Inoculation of Fruit Trees with Full-Length Infectious cDNA Clones of RNA Viruses.

Long life cycle and lack of efficient and robust virus inoculation technique are the major technical challenges for studying virus infection in perennial woody plants such as fruit trees. Biolistic technology also called particle bombardment is a physical approach that can directly introduce virions or viral full-length cDNA infectiousclones into target cells and tissues by high velocity microcarrier particles. The flexibility and high efficiency of the biolistic inoculation method facilitate research on fruit tree virology and the screening and identification of fruit tree germplasms resistant to viruses. Here, we describe a detailed protocol for the biolistic inoculation of peach with of a cDNA infectious clone of Plum pox virus (PPV) using the Helios gene gun, a biolistic particle delivery system.

Estimation of Biomass Availability in Panglao Island Using SENTINEL-2 MSI

Remote Sensing (RS) technology using SENTINEL-2 Multispectral Instrument (MSI) imagery was used in the estimation of residual biomass’ available energy potential. The estimation was done in Panglao Island, within the province of Bohol, Philippines. Estimation of biomass availability was processed using Geographical Information System (GIS) software incorporating the calculation of Normalized Difference Vegetation Index (NDVI) to extract information on land resources and its spatial distribution. It was found that the majority of vegetation cover on the island is in the form of perennial woody plants and coconut trees. Coconut production on the island of Panglao contributed 1.26% of the total cultivation area for the province based on processed captures of Sentinel-2 imagery. The residue concentration amounted to 2,865 tons of coconut residues based on the RPR method. This amount of residues can be translated to 52.92 TJ of theoretical energy potential. The result of this study may serve as a baseline for the locality to consider the utilization of agricultural residues such as coming from coconut trees to support the use of indigenous resources for energy generation.

Overexpression of Plasma Membrane H+-ATPase in Guard Cells Enhances Light-Induced Stomatal Opening, Photosynthesis, and Plant Growth in Hybrid Aspen.

Stomata in the plant epidermis open in response to light and regulate CO2 uptake for photosynthesis and transpiration for uptake of water and nutrients from roots. Light-induced stomatal opening is mediated by activation of the plasma membrane (PM) H+-ATPase in guard cells. Overexpression of PM H+-ATPase in guard cells promotes light-induced stomatal opening, enhancing photosynthesis and growth in Arabidopsis thaliana. In this study, transgenic hybrid aspens overexpressing Arabidopsis PM H+-ATPase (AHA2) in guard cells under the strong guard cell promoter Arabidopsis GC1 (AtGC1) showed enhanced light-induced stomatal opening, photosynthesis, and growth. First, we confirmed that AtGC1 induces GUS expression specifically in guard cells in hybrid aspens. Thus, we produced AtGC1::AHA2 transgenic hybrid aspens and confirmed expression of AHA2 in AtGC1::AHA2 transgenic plants. In addition, AtGC1::AHA2 transgenic plants showed a higher PM H+-ATPase protein level in guard cells. Analysis using a gas exchange system revealed that transpiration and the photosynthetic rate were significantly increased in AtGC1::AHA2 transgenic aspen plants. AtGC1::AHA2 transgenic plants showed a>20% higher stem elongation rate than the wild type (WT). Therefore, overexpression of PM H+-ATPase in guard cells promotes the growth of perennial woody plants.

Effects of ploidy variation on DNA methylation and gene expression in Pear (Pyrus communis L.)

Polyploid plants of fruit trees are generally characterized by dwarf growth, larger organs, and strong resistance to disease. They are therefore of great value in fruit breeding. Plant epigenetics generally has the forms of DNA methylation, RNA interference, and histone modification. The mechanisms of phenotypic variation and the physiological characteristics of plant polyploids are closely related to epigenetics. However, there have been few studies examining the relationship between DNA methylation and polyploidization in perennial woody plants. In this study, we compared the DNA methylation of unconverted diploids (q2x-1), tetraploids (4x-1, 4x-2) and diploid reference (2x-1) by methylation-sensitive amplification polymorphism (MSAP). The total methylation level of q2x-1, 4x-1, and 4x-2 was higher than that of 2x-1. The total methylation level of q2x-1 was higher than that of 4x-1 and 4x-2. Compared with 2x-1, the methylation pattern was mainly maintenance of methylation in q2x-1, 4x-1, and 4x-2, but the trend of demethylation of q2x-1, 4x-1, and 4x-2 was greater than that of methylation. Compared with q2x-1, the methylation pattern in 4x-1 and 4x-2 is also mainly maintaining methylation, but the trend of demethylation in 4x-1 and 4x-2 is less than that of methylation. The results of BLAST homology comparison and expression verification showed that the ploidy change of plants may affect the expression of genes related to adenosine triphosphate binding, RNA binding, arginine biosynthesis, and cell shape regulation, as well as promoting the polarization growth of leaf epidermis, auxin mediation, and RNA modification by causing a change of DNA methylation. This study provides a theoretical basis for studying the molecular mechanisms of plant ploidy change from the perspective of epigenetics.

A mutation in the promoter of the arabinogalactan protein 7-like gene PcAGP7-1 affects cell morphogenesis and brassinolide content in pear (Pyrus communis L.) stems.

Dwarfing rootstocks and dwarf cultivars are urgently needed for modern pear cultivation. However, germplasm resources for dwarfing pear are limited, and the underlying mechanisms remain unclear. We previously showed that dwarfism in pear is controlled by the single dominant gene PcDw (Dwarf). We report here that the expression of PcAGP7-1 (ARABINOGALACTAN PROTEIN 7-1), a key candidate gene for PcDw, is significantly higher in dwarf-type pear plants because of a mutation in an E-box in the promoter. Electrophoretic mobility shift assays and transient infiltration showed that the transcription factors PcBZR1 and PcBZR2 could directly bind to the E-box of the PcAGP7-1 promoter and repress transcription. Moreover, transgenic pear lines overexpressing PcAGP7-1 exhibited obvious dwarf phenotypes, whereas RNA interference pear lines for PcAGP7-1 were taller than controls. PcAGP7-1 overexpression also enhanced cell wall thickness, affected cell morphogenesis, and reduced brassinolide (BL) content, which inhibited BR signaling via a negative feedback loop, resulting in further dwarfing. Overall, we identified a dwarfing mechanism in perennial woody plants involving the BL-BZR/BES-AGP-BL regulatory module. Our findings provide insight into the molecular mechanism of plant dwarfism and suggest strategies for the molecular breeding of dwarf pear cultivars.

(+)-Catechin, epicatechin and epigallocatechin gallate are important inducible defensive compounds against Ectropis grisescens in tea plants.

The tea plant, Camellia sinensis (L.) O. Kuntze, is an economically important, perennial woody plant rich in catechins. Although catechins have been reported to play an important role in plant defences against microbes, their roles in the defence of tea plants against herbivores remain unknown. In this study, we allowed the larvae of Ectropis grisescens, a leaf-feeding pest, to feed on the plants, and alternatively, we wounded the plants and then treated them with E. grisescens oral secretions (WOS). Both approaches triggered jasmonic acid-, ethylene- and auxin-mediated signalling pathways; as a result, plants accumulated three catechin compounds: (+)-catechin, epicatechin and epigallocatechin. Not only was the mass of E. grisescens larvae fed on plants previously infested with E. grisescens or treated with WOS significantly lower than that of larvae fed on controls, but also artificial diet supplemented with epicatechin, (+)-catechin or epigallocatechin gallate reduced larval growth rates. In addition, the exogenous application of jasmonic acid, ethylene or auxin induced the biosynthesis of the three catechins, which, in turn, enhanced the resistance of tea plants to E. grisescens, leading to the coordination of the three signalling pathways. Our results suggest that the three catechins play an important role in the defences of tea plants against E. grisescens.