Pear Tissue Research Articles

Identification and expression analysis of the PbrMLO gene family in pear, and functional verification of PbrMLO23

Mildew resistance locus O (MLO) is a plant-specific gene family that plays an important role in the growth and development of plants and their interactions with the environment. However, the available information on this gene family in pear is limited. Here, 24 PbrMLO genes were identified and divided into five subfamilies (I, II, III, IV and V). Whole-genome duplication (WGD) and dispersed duplication contributed to the expansion of the PbrMLO family. In addition, gene expression analysis revealed that PbrMLO genes were distributed in various pear tissues, suggesting their diverse functions. We selected PbrMLO23 for further functional analysis. Expression profile analysis by qRT-PCR showed that PbrMLO23 was highly expressed in pollen. Subcellular localization analysis showed that PbrMLO23 was located on the plasma membrane. When the expression level of PbrMLO23 was knocked down by using antisense oligonucleotides, pollen tube lengths increased, indicating that PbrMLO23 plays a functional role in inhibiting pollen tube growth. In summary, these results provide evolutionary insight into PbrMLO and its functional characteristics and lay a foundation for further analysis of the functions of PbrMLO members in pear.

Spatial frequency domain imaging for determining absorption and scattering properties of bruised pears based on profile corrected diffused reflectance

Curved surface of fruit has a great influence on the measurement of absorption (μa) and reduced scattering coefficients (μ’s) by using the spatial frequency domain imaging (SFDI) technique. In this study, a developed SFDI system was used to conduct phase-measuring profilometry (PMP) to obtain the surface height of tested object. Monte Carlo (MC) simulation was conducted on planar and spherical geometric models, and the correction formula for diffuse reflectance (Rd) was then determined by simulation results and validated by tilt standard reflector. The Rd correction effect on estimating μa and μ’s was revealed by five semi-spherical phantoms, which turned out that both the accuracy and uniformity were substantially improved, with the relative error range of 0.78 %-11.84 % and 2.83 %-8.95 %, and standard deviation range of 1.89 × 10−5 mm-1-1.42 × 10-3 mm-1 and 1.76 × 10-4 mm-1-8.17 × 10-3 mm-1 for corrected μa and μ’s respectively. Finally, the proposed Rd correction method was applied to the bruise detection in pears, the comparisons of μa and μ’s maps between normal and bruised pears were conducted. The results revealed that the area around the highest point of normal pear contour was easily to be identified as bruised area before Rd correction; the μa and μ’s maps for normal pear were more uniform, and for bruised pears after the correction, and the injured area was highlighted for bruised pears. The profile correction method proposed in this study, coupled with the SFDI technique, was essential for precise measurement of μa and μ’s of pear tissues, resulting in less misclassification for bruise detection of pears.

Genome-wide identification and expression analysis of the pear autophagy-related gene PbrATG8 and functional verification of PbrATG8c in Pyrus bretschneideri Rehd.

Genome-wide identification, tissue-specific and stress expression analyses and functional characterization of PbrATG8s genes were conducted and the role of PbrATG8c in Botryosphaeria dothidea resistance was further investigated. Autophagy plays an important role in plant growth, development and stress tolerance. ATG8 has been reported to be an autophagy marker in many species. However, there is little information regarding ATG8 family members in pear (Pyrus bretschneideri Rehd). We performed a genome-wide analysis and identified nine PbrATG8 gene family members in pear. Phylogenetic analysis showed that PbrATG8 genes clustered into four major groups (Groups I-IV). Eight PbrATG8 genes were successfully mapped to 6 of the 17 chromosomes of the pear genome. The synteny results showed that two pairs are collinear. Gene expression data showed that all genes were differentially expressed in a range of pear tissues. Transcript analysis of PbrATG8 genes under dehydration, salt and pathogen infection stresses revealed that PbrATG8c responded to all test stresses. The PbrATG8c protein was localized in the nucleus and membrane. The silencing of PbrATG8c decreased the resistance to Botryosphaeria dothidea in pear. This study provides insights and rich resources for subsequent investigations of autophagy in pear.

Effect of Activated Carbon on Rooting of Tissue Culture Seedlings of Qiuzi Pear

In order to improve the rooting rate of Qiuzi pear tissue culture seedlings, this study took 'sorb' as experimental material, based on Qiuzi pear rooting tissue culture medium (1/2MS+IBA 0.5 mg/L), and added different concentrations of activated carbon (AC): 0.25 g/L, 0.50 g/L, 0.75 g/L, 1.00 g/L. The results showed that the rooting rate, rooting number and root length of tissue culture seedlings cultured with activated carbon were significantly higher than those of the control group. The most suitable medium for rooting Qiuzi pear was 1/2MS+IBA 0.5 mg/L+AC 1.00 g/L, and the rooting rate of the treated sorb tissue culture seedlings reached 90%, which could obviously promote the growth of Qiuzi pear tissue culture. The results provide a theoretical basis for improving the rooting rate and survival rate of tissue culture seedlings of pear plants, and provide a reference for the establishment of rapid propagation system of woody plants.

Detection of ‘Candidatus Phytoplasma pyri’in different pear tissues and sampling time by PCR-RFLP analyses

Aims: In this study, the best sampling time and tissues for phytoplasma detection in twenty pear trees (cv. Deveci) infected by ‘Candidatus Phytoplasma pyri’, causal agent of pear decline disease, in Bursa province of Turkey were investigated.Methods and Results: Sampling was done throughout the year in leaf midribs, shoot and root tissues, where as the flower tissues were tested once a year in March and fruit tissues in September. All samples were analyzed by nested-PCR using P1/P7 and fU5/rU3 universal primer pairs. Nested PCR products were digested with RsaI and SspI restriction enzymes. The results revealed that the detection rate of ‘Ca. P. pyri’ in different plant tissues was greatly depending on the sample collection period. The fruit tissues, which were only sampled in September due to the ripening time of Deveci pear cultivar in Bursa, showed the highest detection rate of ‘Ca. P. pyri’ (100%) followed by flower tissues (75%). The average detection rate in root, shoot tissues and leaf midribs was found as 43.75, 39.58 and 16.25%, respectively. The present results showed that the best plant tissues for detecting ‘Ca. P. pyri’ in pear trees were fruit columella and flowers. The highest detection rate of this phytoplasma in root tissues was found from November to March, whereas it could be detected whole year around except summer months in shoot samples in Turkey.Conclusions: For 'Candidatus Phytoplasma pyri', detection, if there is no seasonal limitation for testing, the most suitable tissues are fruits and flowers. When it comes to testing throughout the year, the most suitable tissues were determined as the root, the phloem and cambium layer of the shoots and the leaves, respectively.Significance and Impact of the Study: This study on seasonal variations of ‘Candidatus Phytoplasma pyri’ in different pear tissues has been first time investigated in Turkey. This preliminary data provides important knowledge on molecular detection of Ca. P. pyri, causal agent of pear decline disease for further studies and sertification-quarantine programmes of pear trees in Turkey.

Development of Apple Tissue Based Biocathode and MWCNT−Pt−Au Nanomaterial Based Bioanode Biofuel Cell

A biofuel cell (BFC) was fabricated by combining multiwalled carbon nanotube -platinum-gold (MWCNT−Pt−Au) hybrid nanomaterial, glucose oxidase (GOx) and benzoquinone included carbon felt electrode (CFE) bioanode with apple tissue included CFE biocathode. The working parameters of bioanode were optimized both experimentally and chemometrically. For the biocathode, apple, banana and pear tissues were tried and best power output was obtained with apple tissue. By combining MWCNT−Pt−Au/GOx/CFE bioanode with apple tissue based biocathode, single cell, double cell with membrane and with salt-bridge BFCs were formed. The best power output with highest current density were obtained with single cell BFC.

‘Gigante’ cactus pear cultivated at different population densities in a mechanizable arrangement

ABSTRACT Cactus pear is a crop adapted to the climatic conditions of the Brazilian semiarid region, so it has contributed to the socioeconomic development of this region. The objective of this study was to evaluate the response of ‘Gigante’ cactus pear cultivated at different population densities in a mechanizable arrangement. The experimental design was in randomized blocks, with six population densities: 22,857; 34,286; 51,428; 62,857; 80,000 and 95,000 plants ha-1 and four repetitions. The following variables were evaluated: plant height, number of cladodes, cladode length, cladode width and cladode area index, green and dry matter yields, extraction/export of nutrients and soil chemical characteristics. Increase in population density in a mechanizable arrangement decreases the number of cladodes and increases the cladode area index. The maximum green and dry matter yield of cactus pear cultivated in arrangement that allows mechanization is expected with populations of 69,111.79 and 64,445.91 plants ha-1, respectively. Maximum values of extraction/export of nutrients in cactus pear tissue are expected at intermediate population densities (62,721.52-74,741.93 plants ha-1). Soil potential acidity has maximum value with 64,525.51 plants ha-1.

PbrPOE21 inhibits pear pollen tube growth in vitro by altering apical reactive oxygen species content.

Genome-wide identification, tissue-specific expression analysis and functional characterization of selected genes containing the pear Pollen Olea europaea I domain reveal their roles in pollen tube growth. Genes containing the Pollen Olea europaea I (POE) domain play crucial roles in diverse growth and developmental processes. Nevertheless, the specific functions of POE family members in progression of pollen tube growth (PTG) remain uncharacterized. We identified 45 PbrPOE genes in the pear (Pyrus bretschneideri) genome, clustered into seven subclasses. PbrPOE genes contained 1 to 11 exons and 0 to 10 introns, with exon/intron structure mostly conserved within each subclass. Whole-genome duplication has mainly contributed to the duplication pattern of PbrPOE genes in pear. Expression profiles of 45 PbrPOE genes in 12 different pear tissues revealed that six PbrPOE genes (PbrPOE6, 12, 21, 29, 35 and 41) of subclass B were highly expressed during the growth of the pear pollen tube in vitro. PbrPOE21 was selected for further functional analysis on the basis of its high and differential expression pattern in pollen. Antisense oligodeoxynucleotide assays demonstrated that PTG was augmented in vitro when PbrPOE21 expression was significantly inhibited. Moreover, pollen tube length in vitro was reduced when PbrPOE21 was transitorily over-expressed using particle bombardment technology. Exogenous PbrPOE21 recombinant protein inhibited PTG in vitro at an optimum concentration of 1.8µM. PbrPOE21 also affected reactive oxygen species content in the pear pollen tube apex. We suggest that PbrPOE21 inhibits PTG in vitro by altering apical reactive oxygen species content.

Ultrastructure observation and transcriptome analysis of Penicillium expansum invasion in postharvest pears

Abstract Pears are one of the most essential fruit worldwide, they are susceptible to Penicillium expansum infection during postharvest storage, which results in high economic losses. Due to the dearth of information involving the mechanisms of infection of P. expansum in pear fruit it is very important to clarify its pathogenicity. In this study, the fungus strain was isolated from rotten pears and identified as P. expansum, which has strong pathogenicity. The results from SEM revealed that P. expansum relies on the growth of spores or the secretion of filamentous materials to degrade the cell wall of infected pear tissues. In addition, it was found that tissues were completely damaged after 24 h of infection. The RNA-seq results of P. expansum in infected pear tissue suggested that total differentially expressed genes (DEGs) were grouped into 4 profiles due to an upward trend in their gene expression patterns using the STEM software. The DEGs of the 4 profiles were involved in extracellular enzyme activity, cellular response to reactive oxygen, glutathione metabolic species, and polysaccharide metabolic process particularly the plant cell wall degrading enzyme (CWDEs) synthesis pathway. In summary, this research provides a piece of new information with regards to the infection mechanisms of P. expansum on pears, which could be useful in understanding the phenomenon of pathogen -host -fruit interaction and the development of new measures for the control of fungal diseases.

Expression and evolutionary analysis of soluble inorganic pyrophosphatase gene family in pear and four other Rosaceae species

In plants, soluble inorganic pyrophosphatase (PPA) play an indispensable role in inorganic pyrophosphate hydrolysis. However, the expression and the evolutionary history of PPA gene family remain unclear in pear and Rosaceae species. In this study, thirty-nine PPA genes were identified from five Rosaceae species including pear (Pyrus bretschneideri), apple (Malus domestica), peach (Prunus persica), strawberry (Fragaria vesca) and Japanese apricot/mei (Prunus mume). Based on the structural characteristics of the genes and phylogenetic analysis, members of PPA gene family were classified into two main subfamilies (A and B). Whole-genome duplication (WGD) and dispersed gene duplication were the main force, which drove the expansion of PPA gene family in pear and other Rosaceae species. Purifying selection played a dominant role in the evolution of PPA genes. Subcellular localization analysis demonstrated that pear PPA genes located in the cytosol, chloroplasts or near the nuclear envelope. PPA genes showed multiple expression patterns in different pear tissues. Several members of PPA gene family presented particularly higher expression level in only one of the six tissues, such as PbrPPA2, PbrPPA5 and PbrPPA8. Expression analysis showed that five PPA genes were involved in the growth of pear pollen tube, meanwhile four PPA genes could respond to excess of PPi in pear pollen tube. Overall, we established a comprehensive landscape in the functional characterization and evolution of PPA gene family in pear and Rosaceae species, and provided gene expression data for exploring the functional roles of PPA genes in the growth of pear pollen tube.

PbMYB120 Negatively Regulates Anthocyanin Accumulation in Pear.

Subgroup 4 R2R3 MYBs play vital roles in the regulation of anthocyanin biosynthesis. However, there is limited knowledge regarding the functions of MYB repressors in pear (Pyrus × bretschneideri). Here, PbMYB120 was identified as a potential regulator of anthocyanin biosynthesis. A phylogenetic analysis revealed that PbMYB120 was clustered into the FaMYB1-like clade of the subgroup 4 R2R3 MYBs. PbMYB120 was expressed higher in red peels than in green peels in five pear cultivars. PbMYB120 expression was positively correlated with anthocyanin accumulation. However, the transient overexpression of PbMYB120 led to the inhibition of anthocyanin accumulation and PbUFGT1 expression. Promoter binding and activation assays indicated that PbMYB120 binds to the promoter of PbUFGT1 and represses the promoter’s activity. Thus, the inhibition of anthocyanin accumulation by PbMYB120 may be correlated with the repression of PbUFGT1. Furthermore, during anthocyanin induction, the expression levels of anthocyanin activators and PbMYB120 were upregulated. This study demonstrated that PbMYB120 was highly expressed in pear tissues having higher anthocyanin accumulations but acted as a repressor in the regulation of anthocyanin accumulation. PbMYB120 may work coordinately with anthocyanin activators and serve as a balancer of anthocyanin accumulation.

Online assessment of pear firmness by acoustic vibration analysis

Firmness is an important quality indicator of fruit and is closely related to physical structures and mechanical properties. In this study, an online detection system using a laser Doppler vibrometer (LDV) was developed to acquire the acoustic vibration response signals of ‘Cuiguan’ pears for firmness detection. Based on compositional analysis of pear tissue, the predominant components in the process of fruit softening were crude fiber and pectin. Subsequently, different classification models for prediction of pear firmness were established based on sensory evaluation. The results showed that a back propagation neural network (BPNN) method using the elasticity index (EI), peak value at f2 (A) and peak area (S) as input variables had the highest discriminant accuracy. The accuracies of the calibration and validation sets were 93.3 % and 90.5 %, respectively. Moreover, the stiffness in the peeled group obtained by a puncture test was regarded as a dependent variable in quantitative analysis due to its high correlation coefficients with sensory scores and chemical indices in postharvest. In addition, multiple regression models were compared with simple linear regression models. The highest correlation coefficient rp of the prediction set was observed for the BPNN model. In addition, the BPNN method using EI, A, S and the shape index had the best prediction performance. The correlation coefficient rp and RMSEP of the prediction set were 0.832 and 0.277 N mm−1, respectively.

Evolutionary characteristics and expression patterns of miR156 gene family in Korla fragrant pear (Pyrus sinkiangensis Yu)

ABSTRACTThe objective of the study was to understand the evolution characteristics of miR156 gene family and its expression patterns in calyx abscission zone (AZ) tissues of Korla fragrant pear (Pyrus sinkiangensis Yu). miR156 family of Korla fragrant pear (psi-miR156) was obtained through small RNA sequencing. We analysed the mature sequences and precursor sequence, constructed phylogenetic tree, predicted the secondary structure of precursors sequence, analysed their targets, as well as expression patterns. The results showed that miR156 family of Korla fragrant pear comprises 11 precursor sequences and 6 mature sequences. These precursor sequences can form a typical and stable stem-loop structure. Their minimum folding free energy ranges from −77.20 to −7.99 kal•mol−1. Multiple sequence alignment showed that miR156 family was highly conserved. Phylogenetic tree analysis indicated that the genetic relationship of psi-miR156 family was closer to those from apple and Arabidopsis thaliana. Psi-miR156 family was predicted to target SPL (Squamosa promoter-binding protein-like), cysteine protease, trihelix transcription factor. qRT-PCR showed that different members of psi-miR156 family had similar expression tendency in calyx AZ tissue. The expression level of miR156 was significantly increased on the fifth day of the late bloom stage, suggesting that the miR156 family may play a role in calyx persistence of Korla fragrant pear.Abbreviations: AZ: abscission zone; SPL: Squamosa promoter-binding protein-like; PP333: Paclobutrazol; C_1: The collected flowers on the first day of the late bloom stage with GA3 treatment; C_5: The collected flowers on the fifth day of the late bloom stage with GA3 treatment; C_9: The collected flowers on the ninth day of the late bloom stage with GA3 treatment; T_1: The collected flowers on the first day of the late bloom stage with PP333 treatment; T_5: The collected flowers on the fifth day of the late bloom stage with PP333 treatment; T_9: The collected flowers on the ninth day of the late bloom stage with PP333 treatment.

Rapid Detection of Alternaria Species Involved in Pear Black Spot Using Loop-Mediated Isothermal Amplification.

Alternaria species are the most important fungal pathogens that attack various crops as well as fruit trees such as pear and cause black spot disease. Here, a loop-mediated isothermal amplification (LAMP) assay is developed for the detection of Alternaria species. A. alternata cytochrome b (cyt-b) gene was used to design two pairs of primers and amplified a 229-bp segment of Aacyt-b gene. The results showed that LAMP assay is faster and simpler than polymerase chain reaction (PCR). LAMP assay is highly sensitive method for the detection of about 1 pg of genomic DNA of A. alternata by using optimized concentration of MgCl2 (4 mM) in final LAMP reaction. In contrast, the limit of detection was 1 ng of target DNA via conventional PCR. Among the genomic DNA of 46 fungal species, only the tubes containing DNA of Alternaria spp. except A. porri, A. solani, and A. infectoria changed color from orange to yellowish green with SYBR Green I including the main pathogens of pear black spot. The yellowish green color was indicative of DNA amplification. Moreover, LAMP assay was used for testing infected tissues among 22 healthy and diseased pear tissues; the orange color changed to yellowish green for infected tissues only. Altogether, we conclude that cyt-b gene can be used for the detection of Alternaria spp. via LAMP assay, which is involved in pear black spot disease.

Characterization and quantification of individual betalain and phenolic compounds in Mexican and Spanish prickly pear (Opuntia ficus-indica L. Mill) tissues: A comparative study

Betalain and phenolic profiles of whole fruit, pulp and peel of 6 Mexican and Spanish prickly pear (Opuntia ficus-indica L. Mill.) cultivars were characterized and quantified using a single extraction and HPLC-DAD-ESI-QTOF protocol. A total of 14 betalains were detected, where betanin and indicaxanthin were the most abundant. The purple cultivars Spanish Morada and Mexican Pelota showed the highest concentration of betacyanins (1,372-2176 μg/g dry whole fruit), whereas the greatest betaxanthin values were obtained in red Spanish Sanguinos and yellow Mexican Diamante cultivars (435–488 μg/g dry whole fruit). The detected 17 phenolics corresponded mostly to flavonoid (isorhamnetin, quercetin and kaempferol) glycosides and a phenolic acid, piscidic acid. The highest phenolic content was found in Spanish Morada cultivar (49,012 μg/g dry peel). The proposed HPLC methodology is a useful tool for the simultaneous and accurate analyses of betalains and phenolic compounds in O. ficus-indica fruit tissues.

Expression analysis of sorbitol transporters in pear tissues reveals that PbSOT6/20 is associated with sorbitol accumulation in pear fruits

Sorbitol is a primary substrate that is translocated from its source to its sink in pear and apple by sorbitol transporters (SOTs). However, little is known about the expression profiles of SOTs in tree tissues, and their association with sorbitol accumulation. In this study, 64 SOT genes were isolated from the sequenced genomes of six rosaceae trees, which clustered phylogenetically into four groups. Groups I and III contained genes from pome trees, group II those from drupe trees, and group IV those from pome, drupe, and berry trees. A gene duplication analyses showed that the 24 SOT genes of pear arose from tandem, proximal, and dispersed duplications, which differs from their evolution in the other rosaceae fruit trees. A qRT-PCR analysis showed that the PbSOT6/20 gene in group IV is most strongly expressed in the leaf, branch, flower, fruit, and seed of pear. The expression pattern of PbSOT6/20 correlates more strongly with the pattern of sorbitol accumulation in the pear fruits than do those of other SOT genes. A low concentration (100 mg/g) of exogenous sorbitol induced the expression of PbSOT6/20 in the pear fruits, but not in the leaves. These results suggest that PbSOT6/20 is associated with sorbitol accumulation in pear fruits and plays important role in sorbitol translocation from its source to its sink. This study provides new insights into sorbitol translocation mediated by the SOT genes in pear.

Application and Simplification of Cell-Based Equivalent Circuit Model Analysis of Electrical Impedance for Assessment of Drop Shock Bruising in Japanese Pear Tissues

This study was conducted with the objective of applying cell-based electrical equivalent circuit analysis for the assessment of bruising of tissues in Japanese pears after drop tests, as well as to simplify the analysis. The equivalent circuit analysis of electrical impedance values was conducted on the bruised regions of the pear tissues. The analysis showed that the resistance of the protoplasm of the injured tissues slightly increases, and the capacitance of cell membranes and the resistance of apoplastic fluids significantly decrease. Thus, it was theorized that these parameters are influenced by cell membrane destruction. Further, it was found that Cole-Cole plot parameter obtained from the frequency characteristics of the impedance of the tissues can express changes in the apoplastic fluid resistance. These results show that equivalent circuit analysis can be used to assess bruising of pear cells caused by drop shock, and the analysis can be simplified using Cole-Cole plots. We expect these results to aid in the development of physical damage assessment methods for distributed fruits.

Characterizing the expression of translation elongation factor gene EF1α in pear (Pyrus) fruit: evaluation of EF1α as a housekeeping gene

Reference genes are a key factor for the sensitivity and reliability of quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis. The elongation factor gene EF1α encodes a highly conserved ubiquitous protein that functions in the binding of aminoacyl-tRNA to the ribosome during peptide synthesis in eukaryotes, which is proposed for qRT-PCR as an internal reference for its putative housekeeping gene character. However, information about the paralogous copies and expression diversification of EF1α has been neglected and ill defined. In this study, the members of pear (Pyrus) EF1α were explored by mining public data. The family- and/or species-specific members of EF1α in Rosaceae plants or other species revealed by phylogenetic analysis suggested that the specific gene expansion occurred after the family or species diversification. The expression analysis based on the high-throughput sequencing and sequence differences typing provided a high resolution to distinguish the expression among the members of pear EF1α. The EF1α members showed an obviously unstable expression in both pear and apple (Malus × domestica) fruits at different developmental stages, clustered by two conserved expression patterns in pear fruit. The complementary expression among certain pear EF1α members leads to the sum expression of these members having a higher level of expression stability among the fruit at different developmental stages, which can be used as an approach to optimize EF1α as the internal reference. The result can also provide insight into the expression characteristics of pear EF1α in other tissues of pear. In addition, it indicates that any two genes having complementary expression patterns can be used as a reference for qPCR analysis with the high stability of their mean expression value.

A new insight into the evolution and functional divergence of FRK genes in Pyrus bretschneideri.

In plants, plant fructokinases (FRKs) are considered to be the main gateway of fructose metabolism as they can phosphorylate fructose to fructose-6-phosphate. Chinese white pears (Pyrus bretschneideri) are one of the popular fruits in the world market; sugar content is an important factor affecting the quality of the fruit. We identified 49 FRKs from four Rosaceae species; 20 of these sequences were from Chinese white pear. Subsequently, phylogenic relationship, gene structure and micro-collinearity were analysed. Phylogenetic and exon–intron analysis classified these FRKs into 10 subfamilies, and it was aimed to further reveal the variation of the gene structure and the evolutionary relationship of this gene family. Remarkably, gene expression patterns in different tissues or different development stages of the pear fruit suggested functional redundancy for PbFRKs derived from segmental duplication or genome-wide duplication and sub-functionalization for some of them. Additionally, PbFRK11, PbFRK13 and PbFRK16 were found to play important roles in regulating the sugar content in the fruit. Overall, this study provided important insights into the evolution of the FRK gene family in four Rosaceae species, and highlighted its roles in both pear tissue and fruits. Results presented here provide the appropriate candidate of PbFRKs that might contribute to fructose efflux in the pear fruit.

Genome-wide identification of lectin receptor kinases in pear: Functional characterization of the L-type LecRLK gene PbLRK138

Lectin receptor-like kinases (LecRLKs) are membrane-bound receptors that are believed to be involved in biotic and abiotic stress responses. However, little is known about the LecRLK family in pear. In this study, a total of 172 LecRLK genes were first identified in the entire pear genome. The 172 LecRLKs were divided into three types (111 G-, 59 L- and two C-types) based on their structure and phylogenetic relationships. LecRLKs gene expressions were detected in different pear tissues including roots, stems, leaves, flowers and fruits, and the most of the 11 selected LecRLKs exhibited similar expression patterns. Furthermore, six selected LecRLKs were shown to be involved in salt stress response. Overexpression of PbLRK138, an L-type LecRLK, caused cell death and induced expression of defense-related genes in Nicotiana benthamiana. Two deletion mutants containing lectin or transmembrane and serine/threonine kinase domains did not trigger cell death. In addition, only the mutant with the transmembrane domain was localized to the plasma membrane.