Later Stages Of Fruit Development Research Articles

Cytological characteristics of blueberry fruit development

Using the blueberry cultivar "Powderblue" after pollination, fruits at different developmental stages were collected for study. The transverse and longitudinal diameters, individual fruit weight, and fruit water content were measured during their development. Employing tissue sectioning and microscopy techniques, we systematically studied the morphological features and anatomical structures of the fruits and seeds at various developmental stages, aiming to elucidate the cytological patterns during blueberry fruit development. The results of our study revealed that the "Powderblue" blueberry fruit growth and development followed a double "S" curve. Mature "Powderblue" blueberries were blue-black in color, elliptical in shape, with five locules, an inferior ovary, and an average fruit weight of 1.73 ± 0.17 g, and a moisture content of 78.865 ± 0.9%. Blueberry fruit flesh cells were densely arranged with no apparent intercellular spaces, and mesocarp cells accounted for 52.06 ± 7.4% of fruit cells. In the early fruit development stages, the fruit flesh cells were rapidly dividing, significantly increasing in number but without greatly affecting the fruit's morphological characteristics. During the later stages of fruit development, the expansion of the fruit flesh cells became prominent, resulting in a noticeable increase in the fruit's dimensions. Except for the epidermal cells, cells in all fruit tissues showed varying degrees of rupture as fruit development progressed, with the extent of cell rupture increasing, becoming increasingly apparent as the fruit gradually softened. Additionally, numerous brachysclereids (stone cells) appeared in the fruit flesh cells. Stone cells are mostly present individually in the fruit flesh tissue, while in the placental tissue, they often group together. The "Powderblue" blueberry seeds were light brown, 4.13 ± 0.42 mm long, 2.2 ± 0.14 mm wide, with each fruit containing 50–60 seeds. The "Powderblue" seeds mainly consisted of the seed coat, endosperm, and embryo. The embryo was located at the chalazal end in the center of the endosperm and was spatially separated. The endosperm, occupying the vast majority of the seed volume, comprised both the chalazal and outer endosperm, and the endosperm developed and matured before the embryo. As the seed developed, the seed coat was gradually lignified and consisted of palisade-like stone cells externally and epidermal layer cells internally.

Effects of Potassium-Containing Fertilizers on Sugar and Organic Acid Metabolism in Grape Fruits.

To identify suitable potassium fertilizers for grape (Vitis vinifera L.) production and study their mechanism of action, the effects of four potassium-containing fertilizers (complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate) on sugar and organic acid metabolism in grape fruits were investigated. Potassium-containing fertilizers increased the activity of sugar and organic acid metabolism-related enzymes at all stages of grape fruit development. During the later stages of fruit development, potassium-containing fertilizers increased the total soluble solid content and the sugar content of the different sugar fractions and decreased the titratable acid content and organic acid content of the different organic acid fractions. At the ripening stage of grape fruit, compared with the control, complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate increased the total soluble solid content by 1.5, 1.2, 3.5, and 3.4 percentage points, decreased the titratable acid content by 0.09, 0.06, 0.18, and 0.17 percentage points, respectively, and also increased the total potassium content in grape fruits to a certain degree. Transcriptome analysis of the differentially expressed genes (DEGs) in the berries showed that applying potassium-containing fertilizers enriched the genes in pathways involved in fruit quality, namely, carbon metabolism, carbon fixation in photosynthetic organisms, glycolysis and gluconeogenesis, and fructose and mannose metabolism. Potassium-containing fertilizers affected the expression levels of genes regulating sugar metabolism and potassium ion uptake and transport. Overall, potassium-containing fertilizers can promote sugar accumulation and reduce acid accumulation in grape fruits, and potassium sulfate and potassium dihydrogen phosphate had the best effects among the fertilizers tested.

Comparative Transcriptome Analysis Reveals Genes Associated with Alkaloid Diversity in Javanese Long Pepper (Piper retrofractum) Fruits

Alkaloids are a class of secondary metabolites that play multifaceted roles in plant physiology, including defense mechanisms and interactions with other organisms. The alkaloids from Piper retrofractum (Javanese long pepper) fruits offer potential alternatives to synthetic pesticides due to their natural origin and insecticide properties. However, information on particular alkaloid biosynthesis pathways is required to enhance individual alkaloid production via metabolic engineering. Here, we perform HPLC profiling to demonstrate that fruit ripening influences the alkaloid diversity in P. retrofractum. De novo transcriptomic profiling of young, green mature, and red ripened fruits revealed that the piperine biosynthesis pathway genes were highly upregulated in the mature fruits. However, an enhanced accumulation of methyl piperate and guineensine in the ripened fruit was observed, entailing ripening-related differential gene expression to synchronize the alkaloid biosyntheses. Gene expression clustering and functional enrichment analysis identified a large group of genes involved in diverse biosynthetic processes explicitly enriched in the ripened fruits. A cohort of genes encoding for “Alkaloid Biosynthesis”, remarkably upregulated in the ripening fruits, indicates they may function directly in alkaloid diversity during a later stage of fruit development. This study provides the basis for metabolic engineering to enhance alkaloid diversity and production.

Identification and characterisation of MdUGT78T2 as a galactosyltransferase with dual activity on flavonol and anthocyanidin substrates in red-skinned apple fruit (Malus domestica L.).

Anthocyanidin and flavonol glycosides have been linked to the health-promoting effects associated with apple consumption. However, very few enzymes involved in flavonoid glycosylation have been characterised to date. Here, we present the identification and phylogenetic analysis of 234 putative glycosyltransferases involved in flavonoid biosynthesis, and detail the biochemical and structural characterisation of MdUGT78T2 as a strict galactosyltransferase involved in the formation of quercetin-3-O-galactoside and cyanidin-3-O-galactoside, the major glycoconjugates of flavonoids in apple. The enzyme is also active on other flavonoids but with a lower catalytic efficiency. Our data, complemented with gene expression analysis suggest that MdUGT78T2 synthesises the glycoconjugates at both the early and late stages of fruit development. This newly discovered type of catalytic activity can potentially be exploited for in vitro modification of flavonoids to increase their stability in food products and to modify apple fruits and other commercial crops through breeding approaches to enhance their health benefits.

TCP Transcription Factors in Pineapple: Genome-Wide Characterization and Expression Profile Analysis during Flower and Fruit Development

TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors contain specific a basic helix–loop–helix structure, which is a significant factor in the regulation of plant growth and development. TCP has been studied in several species, but no pineapple TCP has been reported to date. Whether they are involved in the development of the flower and fruit in the pineapple remains unclear. In this study, nine non-redundant pineapple TCPs (AcTCPs) were identified. Chromosomal localization, phylogenetics, gene structure, motifs, multiple-sequence alignment, and covariance on AcTCP family members were analyzed. Analysis of promoter cis-acting elements illustrated that the AcTCP gene may be mainly co-regulated by light signal and multiple hormone signals. Analysis of expression characteristics showed a significant increase in AcTCP5 expression at 12 h after ethylene treatment, and significantly higher levels of AcTCP8 and AcTCP9 expression in the pistil than in other floral organs. Meanwhile, the AcTCP4, AcTCP5, AcTCP6, AcTCP7, and AcTCP9 expression levels were downregulated at later stages of fruit development. Transcription factors that may interact with TCP protein in the regulation of flower and fruit development are screened by the protein interaction prediction network, AcTCP5 interacts with AcSPL16, and AcTCP8 interacts with AcFT5 and AcFT6 proteins, verified by Y2H experiments. These findings provide a basis for further exploration of the molecular mechanisms and function of the AcTCP gene in flower and fruit development.

Uncovering the Expansin Gene Family in Pomegranate (Punica granatum L.): Genomic Identification and Expression Analysis

Expansins, which are important components of plant cell walls, act as loosening factors to directly induce turgor-driven cell wall expansion, regulate the growth and development of roots, leaves, fruits, and other plant organs, and function essentially under environmental stresses. In multiple species, many expansin genes (EXPs) have been cloned and functionally validated but little is known in pomegranate. In this study, a total of 33 PgEXPs were screened from the whole genome data of ‘Taishanhong’ pomegranate, belonging to the EXPA(25), EXPB(5), EXLA(1), and EXLB(2) subfamilies. Subsequently, the composition and characteristics were analyzed. Members of the same branch shared similar motif compositions and gene structures, implying they had similar biological functions. According to cis-acting element analysis, PgEXPs contained many light and hormone response elements in promoter regions. Analysis of RNA-seq data and protein interaction network indicated that PgEXP26 had relatively higher transcription levels in all pomegranate tissues and might be involved in pectin lyase protein synthesis, whilst PgEXP5 and PgEXP31 might be involved in the production of enzymes associated with cell wall formation. Quantitative real-time PCR (qRT-PCR) results revealed that PgEXP expression levels in fruit peels varied considerably across fruit developmental phases. PgEXP23 was expressed highly in the later stages of fruit development, suggesting that PgEXP23 was essential in fruit ripening. On the other hand, the PgEXP28 expression level was minimal or non-detected. Our work laid a foundation for further investigation into pomegranate expansin gene functions.

The mechanisms underpinning anthocyanin accumulation in a red-skinned bud sport in pear (Pyrus ussuriensis)

In our study, we demonstrated that histone acetylation promotes anthocyanin accumulation in pears by affecting the expression of key genes. Color is an important trait of horticultural plants, and the anthocyanin content directly affects the nutritional value and commercial value of colored fruits. Therefore, it is important for fruit breeding to cultivate new varieties with bright colors. 'Nanhong' (NH) pear (Pyrus ussuriensis) is a bud sport cultivar of 'Nanguo' (NG) pear. The anthocyanin content in NH pear is significantly higher than that in NG pear, but the underlying molecular mechanism remains unclear. Here, we observed that the anthocyanin biosynthesis structural gene PuUFGT (UDP-glucose: flavonoids 3-O-glucosyltransferase) and an anthocyanin transporter gene PuGSTF6 (glutathione S-transferase) had significantly higher expression levels in NH than in NG pears during the late stages of fruit development. Meanwhile, the R2R3-MYB transcription factor PuMYB110a was also highly expressed in NH pears and could positively regulate the transcription of PuUFGT and PuGSTF6. Overexpression of PuMYB110a in pear increased the fruit anthocyanin content. In addition, despite no significant differences in methylation levels being found in the promoters of PuMYB110a, PuUFGT, and PuGSTF6 when comparing the two varieties, the histone acetylation levels of PuMYB110a were significantly higher in NH pear compared with those in NG pear. Our findings suggest a mechanism for anthocyanin accumulation in NH fruit.

Integrative Analysis of Metabolome and Transcriptome Reveals Molecular Insight into Metabolomic Variations during Hawthorn Fruit Development.

Hawthorn (Crataegus pinnatifida var. major), a cultivated fruit tree, is native and unique to China. Its fruits have high nutritional, health, and medicinal values. However, the development and ripening process of hawthorns is accompanied by dramatic changes in flavor, aroma, and bioactive phytochemicals, which are the fundamental factors that contribute to the potential health benefits and establishment of fruit quality. Therefore, an exploration of the dynamic changes in metabolites and their regulatory networks during the development of hawthorn fruits can elucidate the formation mechanisms of active substances in hawthorn fruits. In this study, we used a broad targeted metabolomics approach to identify and analyze the dynamics of metabolites in hawthorn fruits at five developmental stages. The results revealed 998 primary and secondary metabolites that were classified into 15 categories. The accumulation levels of most sugars increased during fruit development and then accelerated at the fruit ripening stage. The accumulation levels of a few organic acids (e.g., citric acid, isocitric acid, and quinic acid) continuously increased. Many organic acids exhibited significant decreasing trends. Among the 561 secondary metabolites detected, 189 were phenolic acids and 199 were flavonoids. The levels of many flavonoids were significantly reduced at later stages of fruit development; in contrast, the levels of two anthocyanins significantly increased during fruit ripening. Correlation analysis revealed that there is a certain correlation within and between primary as well as secondary metabolites during fruit development. Furthermore, the integration of metabolomic and transcriptomic data in this study revealed that changes in the expression of some differentially expressed genes (DEGs) were associated with the accumulation of metabolites such as sugars, organic acids, and flavonoids, e.g., the upregulated expression levels of CS (citrate synthase) genes were consistent with the continued accumulation of citric acid. Overall, this study demonstrates the metabolic changes that occur during the development of hawthorn fruit, explores the molecular mechanisms that underlie metabolite changes during fruit development, and lays a strong theoretical foundation for the improvement of hawthorn fruit quality and the development of functional components.

Flower Thinning Improves Fruit Quality and Oil Composition in Camellia oleifera Abel

Camellia oleifera is a woody oil tree with overlapping flower bud differentiation and fruit maturation. Therefore, mechanical harvesting of fruits leads to flower abscission. The present study investigated the effects of flower number per tree on fruit growth, yield, nutrient accumulation, and oil fatty acid composition in C. oleifera. Here, we set different flower numbers per tree by thinning flowers. Heavy flower thinning (T2 and T3) significantly reduced fruit yield and the proportion of palmitic, palmitoleic, linoleic, and linolenic acid in fatty acids compared with other treatments. However, heavy thinning favored an increase in fruit size and weight, seed and dry kernel rate of fresh fruit, soluble protein and oil accumulation in seeds, and the proportion of oleic acid and stearic acid in fatty acids, and it had no significant effect on oil yield per tree compared with light thinning (T1) and control (T0). T2 and T3 decreased soluble sugar content in the kernels at the later stage of fruit development (260–320 days after full bloom (DAFB)) in contrast to the rapid fruit growth period (200–230 DAFB). As the crop load decreased, fruit ABA content increased continuously during 260–320 DAFB, while fruit IAA content increased during 260–300 DAFB and then decreased during 310–320 DAFB. These data suggest that the abscission of a few flowers during mechanical harvesting will not affect fruit production efficiency in C. oleifera.

Transcriptomic profiling analysis to identify genes associated with PA biosynthesis and insolubilization in the late stage of fruit development in C-PCNA persimmon

PA-enhanced content causes astringency in persimmon fruit. PCNA persimmons can lose their astringency naturally and they become edible when still on the tree, which allows for conserves of physical and financial resources. C-PCNA persimmon originates in China. Its deastringency trait primarily depends on decreased PA biosynthesis and PA insolubilization at the late stage of fruit development. Although some genes and transcription factors that may be involved in the deastringency of C-PCNA persimmon have been reported, the expression patterns of these genes during the key deastringency stage are reported less. To investigate the variation in PA contents and the expression patterns of deastringency-related genes during typical C-PCNA persimmon ‘Xiaoguo-tianshi’ fruit development and ripening, PA content and transcriptional profiling were carried out at five late stages from 70 to 160 DAF. The combinational analysis phenotype, PA content, and DEG enrichment revealed that 120–140 DAF and 140–160 DAF were the critical phases for PA biosynthesis reduction and PA insolubilization, respectively. The expression of PA biosynthesis-associated genes indicated that the downregulation of the ANR gene at 140–160 DAF may be associated with PA biosynthesis and is decreased by inhibiting its precursor cis-flavan-3-ols. We also found that a decrease in acetaldehyde metabolism-associated ALDH genes and an increase in ADH and PDC genes might result in C-PCNA persimmon PA insolubilization. In addition, a few MYB-bHLH-WD40 (MBW) homologous transcription factors in persimmon might play important roles in persimmon PA accumulation. Furthermore, combined coexpression network analysis and phylogenetic analysis of MBW suggested that three putative transcription factors WD40 (evm.TU.contig1.155), MYB (evm.TU.contig8910.486) and bHLH (evm.TU.contig1398.203), might connect and co-regulate both PA biosynthesis and its insolubilization in C-PCNA persimmon. The present study elucidated transcriptional insights into PA biosynthesis and insolubilization during the late development stages based on the C-PCNA D. kaki genome (unpublished). Thus, we focused on PA content variation and the expression patterns of genes involved in PA biosynthesis and insolubilization. Our work has provided additional evidence on previous knowledge and a basis for further exploration of the natural deastringency of C-PCNA persimmon.

Yerel Zeytin Çeşitlerindeki Pomolojik Değişimlerin Farklı Hasat Zamanlarında Belirlenmesi

Olive (Olea europaea L.) is an important oil producing fruit species and it has been cultivated since ancient times. Turkey is rich in local olive varieties and it is necessary to determine their pomological parameters. The aim of the present study was to determine the pomological characteristics of five olive varieties (Çekişte, Memecik, Yamalak sarısı, Eşek zeytini, Gemlik) at five harvest periods (H1-H5) throughout the fruit development period. Olives were collected from an orchard in Aydın at monthly intervals between July and November 2019. During fruit development and ripening, 10 pomological variables (fruit width and length, seed width and length, fruit and seed weight, flesh weight, flesh/seed ratio, flesh firmness and fruit moisture content) were measured. All pomological variables exhibited significant differences between harvest periods and varieties. While fruit ripening indices of the varieties increased over time, level of change differed among the varieties. During fruit ripening of olive varieties, fruit length and width, fruit weight, seed length and width, fruit flesh weight and flesh/seed ratio increased significantly, while flesh firmness and fruit water contents decreased. Seed weight increased between H1-H3 periods, but it did not show a significant change at the later stages of fruit development. These results show that important physiological changes occur starting from the pit hardening of the olive varieties and continue throughout the fruit growth and ripening.

SlMIR164A regulates fruit ripening and quality by controlling SlNAM2 and SlNAM3 in tomato.

SummaryMiRNAs are important posttranscriptional regulators of plant development. Many miRNAs, such as the conserved miR164 species, are encoded by families of MIRNA genes, but the specific roles of individual MIRNA genes are largely undefined. Here, we characterize the functions and regulatory mechanisms of SlMIR164A, one of the primary genes of Sly‐miR164, in tomato. We show that SlMIR164A is preferentially expressed at late stages of fruit development and plays a vital role in controlling fruit ripening and quality. Loss of function of SlMIR164A by CRISPR/Cas9‐mediated mutagenesis results in accelerated fruit ripening and enhanced chloroplast development, which leads to altered sugar and organic acid contents and affects the nutritional quality of fruits. We also show that SlMIR164A modulates fruit ripening and quality through specific target genes, SlNAM2 and SlNAM3, which control key regulators of chloroplast function and fruit ripening processes. MIR164 genes have been shown to play conserved roles in regulating organ ageing, such as leaf senescence and fruit ripening, in a variety of plants, but whether and how their family members in tomato exert the same function remain to be elucidated. Our results reveal a previously undiscovered role of SlMIR164A in ripening control, which will further our understanding of the actions of MIR164 family, as well as the mechanisms of fruit ripening and quality control in tomato. Moreover, as loss of SlMIR164A exhibits minor impacts on organ morphology, our results can be leveraged in tomato breeding for specific manipulation of fruit ripening and quality to facilitate tomato improvement in agriculture.

Systematic Analysis and Expression Profiles of the 4-Coumarate: CoA Ligase (4CL) Gene Family in Pomegranate (Punica granatum L.).

4-Coumarate:CoA ligase (4CL, EC6.2.1.12), located at the end of the phenylpropanoid metabolic pathway, regulates the metabolic direction of phenylpropanoid derivatives and plays a pivotal role in the biosynthesis of flavonoids, lignin, and other secondary metabolites. In order to understand the molecular characteristics and potential biological functions of the 4CL gene family in the pomegranate, a bioinformatics analysis was carried out on the identified 4CLs. In this study, 12 Pg4CLs were identified in the pomegranate genome, which contained two conserved amino acid domains: AMP-binding domain Box I (SSGTTGLPKGV) and Box II (GEICIRG). During the identification, it was found that Pg4CL2 was missing Box II. The gene cloning and sequencing verified that this partial amino acid deletion was caused by genome sequencing and splicing errors, and the gene cloning results corrected the Pg4CL2 sequence information in the ‘Taishanhong’ genome. According to the phylogenetic tree, Pg4CLs were divided into three subfamilies, and each subfamily had 1, 1, and 10 members, respectively. Analysis of cis-acting elements found that all the upstream sequences of Pg4CLs contained at least one phytohormone response element. An RNA-seq and protein interaction network analysis suggested that Pg4CL5 was highly expressed in different tissues and may participate in lignin synthesis of pomegranate. The expression of Pg4CL in developing pomegranate fruits was analyzed by quantitative real-time PCR (qRT-PCR), and the expression level of Pg4CL2 demonstrated a decreasing trend, similar to the trend of flavonoid content, indicating Pg4CL2 may involve in flavonoid synthesis and pigment accumulation. Pg4CL3, Pg4CL7, Pg4CL8, and Pg4CL10 were almost not expressed or lowly expressed, the expression level of Pg4CL4 was higher in the later stage of fruit development, suggesting that Pg4CL4 played a crucial role in fruit ripening. The expression levels of 4CL genes were significantly different in various fruit development stages. The results laid the foundation for an in-depth analysis of pomegranate 4CL gene functions.

MdMADS6 Recruits Histone Deacetylase MdHDA19 to Repress the Expression of the Carotenoid Synthesis-Related Gene MdCCD1 during Fruit Ripening.

Fruit ripening is regulated by epigenetic modifications and transcription factors, which may function independently or as protein complexes. Our previous study showed that the apple histone deacetylase19 (MdHDA19) suppresses fruit ripening through the deacetylation of histones in related genes. Here, a MADS-box transcription factor (MdMADS6) was identified using a yeast two-hybrid (Y2H) assay as a candidate protein that interacts with MdHDA19 during apple fruit ripening. Furthermore, Y2H, bimolecular fluorescence complementation (BiFC) and pull-down assays were used to confirm the interaction between MdHDA19 and MdMADS6. Agrobacterium-mediated transient transformation and yeast one-hybrid assays showed that MdMADS6 promoted carotenoid accumulation in apple fruit by acting on the downstream target genes related to carotenoid biosynthesis. In summary, we conclude that, in the early stages of fruit development, the expression of MdMADS6 was maintained at lower levels, where it interacted with MdHDA19 to form a protein complex that inhibited the expression of the downstream genes. At the late stages of fruit development, active expression of MdMADS6 dissociated the protein complex of MdMADS6 and MdHDA19 and consequently promoted the expression of carotenoid biosynthesis genes as well as carotenoid accumulation.

Analyses of key gene networks controlling carotenoid metabolism in Xiangfen 1 banana

BackgroundBanana fruits are rich in various high-value metabolites and play a key role in the human diet. Of these components, carotenoids have attracted considerable attention due to their physiological role and human health care functions. However, the accumulation patterns of carotenoids and genome-wide analysis of gene expression during banana fruit development have not been comprehensively evaluated.ResultsIn the present study, an integrative analysis of metabolites and transcriptome profiles in banana fruit with three different development stages was performed. A total of 11 carotenoid compounds were identified, and most of these compounds showed markedly higher abundances in mature green and/or mature fruit than in young fruit. Results were linked to the high expression of carotenoid synthesis and regulatory genes in the middle and late stages of fruit development. Co-expression network analysis revealed that 79 differentially expressed transcription factor genes may be responsible for the regulation of LCYB (lycopene β-cyclase), a key enzyme catalyzing the biosynthesis of α- and β-carotene.ConclusionsCollectively, the study provided new insights into the understanding of dynamic changes in carotenoid content and gene expression level during banana fruit development.

Effects of exogenous KT and BA on fruit quality in strawberry (Fragaria vesca)

ABSTRACT Due to developing production methods and increasing consumption levels, improvement of fruit quality has become a focus of research. Cytokinins are important hormones that affect fruit quality. In this study, exogenous KT (Kinetin) and BA (6-Benzylaminopurine) were applied 1, 3, 5, 7 and 9 days after pollination to study the effect of cytokinins on the quality of strawberry (Fragaria vesca) fruit. The results showed that exogenous KT and BA significantly increased the weight and soluble sugar content of strawberry fruit at late stages of fruit development (27 and 31 DAP). KT and BA treatments up-regulated the expression levels of FvePAL6, FveCHS, FveMYB1, and FveMYB10 at 31 DAP, thus increasing the anthocyanin content. At the red fruit stage, the anthocyanin content of fruits treated with KT and BA were 1.59 and 1.45 times, respectively, higher than that of the control. KT and BA elevated the levels of antioxidants such as ascorbic acid and total phenolics. Also, KT and BA increased the content of myricetin, quercetin, and kaempferol. In addition, KT and BA reduced the relative contents of several aromatic substances. Our results indicate that KT and BA treatments had a significant effect on the improvement of strawberry fruit quality.

Transcriptomic analysis reveals anthocyanin biosynthesis regulation in blueberry (Vaccinium ashei) fruit

Blueberry (Vaccinium ashei) is a popular fruit due to its high anthocyanin content. This study aimed to analyze the transcriptome profile of V. ashei cv. ‘Brightwell’ fruits at different stages of development. A total of 314.26 GB of clean data were obtained and de novo assembled into 254 196 unigenes. In comparisons between the early and late stages of fruit ripening, 27 genes (including PAL, CHS, F3H, F3′H, F3′5′H, LDOX, etc.) were found to cover the main steps in the anthocyanin biosynthesis pathway. Most of these genes were highly expressed in the late stage of fruit development, suggesting that anthocyanins mainly accumulate in the late stage. During the late stage of fruit development, most structural and regulatory genes such as F3′5′H and F3′H, which are involved in the anthocyanin biosynthetic pathway, were upregulated, causing the fruit to turn blue. Decreased expression of a large number of chloroplast-related genes during the fruit ripening period could explain why the green fruit color fades over time. Additionally, abscisic acid and ethylene may play positive roles in promoting fruit ripening and anthocyanin accumulation. This research reveals the transcriptomic characteristics of immature and mature fruits and enhances our understanding of the molecular mechanisms of anthocyanin biosynthesis and accumulation in blueberry fruit.

Comparative transcriptome analysis reveals key genes potentially related to organic acid and sugar accumulation in loquat.

Organic acids and sugars are the primary components that determine the quality and flavor of loquat fruits. In the present study, major organic acids, sugar content, enzyme activities, and the expression of related genes were analyzed during fruit development in two loquat cultivars, 'JieFangZhong' (JFZ) and 'BaiLi' (BL). Our results showed that the sugar content increased during fruit development in the two cultivars; however, the organic acid content dramatically decreased in the later stages of fruit development. The differences in organic acid and sugar content between the two cultivars primarily occured in the late stage of fruit development and the related enzymes showed dynamic changes in activies during development. Phosphoenolpyruvate carboxylase (PEPC) and mNAD malic dehydrogenase (mNAD-MDH) showed higher activities in JFZ at 95 days after flowering (DAF) than in BL. However, NADP-dependent malic enzyme (NADP-ME) activity was the lowest at 95 DAF in both JFZ and BL with BL showing higher activity compared with JFZ. At 125 DAF, the activity of fructokinase (FRK) was significantly higher in JFZ than in BL. The activity of sucrose synthase (SUSY) in the sucrose cleavage direction (SS-C) was low at early stages of fruit development and increased at 125 DAF. SS-C activity was higher in JFZ than in BL. vAI and sucrose phosphate synthase (SPS) activities were similar in the two both cultivars and increased with fruit development. RNA-sequencing was performed to determine the candidate genes for organic acid and sugar metabolism. Our results showed that the differentially expressed genes (DEGs) with the greated fold changes in the later stages of fruit development between the two cultivars were phosphoenolpyruvate carboxylase 2 (PEPC2), mNAD-malate dehydrogenase (mNAD-MDH), cytosolic NADP-ME (cyNADP-ME2), aluminum-activated malate transporter (ALMT9), subunit A of vacuolar H+-ATPase (VHA-A), vacuolar H+-PPase (VHP1), NAD-sorbitol dehydrogenase (NAD-SDH), fructokinase (FK), sucrose synthase in sucrose cleavage (SS-C), sucrose-phosphate synthase 1 (SPS1), neutral invertase (NI), and vacuolar acid invertase (vAI). The expression of 12 key DEGs was validated by quantitative reverese transcription PCR (RT-qPCR). Our findings will help understand the molecular mechanism of organic acid and sugar formation in loquat, which will aid in breeding high-quality loquat cultivars.

The Relationship between Proboscis Length and the Ability of Certain Heteroptera to Damage Macadamia Kernels

The gradual increase in kernel (nut) size as the macadamia seed develops, appears to play a role in the decline of kernel susceptibility to feeding by insects of the suborder Heteroptera. In some cultivars the kernel becomes resistant to feeding before others due to differences in husk and shell thickness (e.g. feeding by Nezara spp.), but species with a long proboscis (e.g. Bathycoelia spp.) could still feed on the kernel after maximum fruit size was reached. The thickness of the husk and shell, and not the hardness of the shell, was the limiting factor in kernel feeding. Bathycoelia distincta Distant (Pentatomidae) and Pseudotheraptus wayi Brown (Coreidae) were the most damaging heteropteran species with respect to the size of the kernel lesions caused. A single feeding incident during early fruit development could cause large necrotic lesions, which totally malformed the kernel. Farnya sp. and Nezara sp. caused only small shallow lesions. During the fruit maturation period, only B. distincta was able to damage the kernel significantly due to its long proboscis. The extent of fruit damage was dependent on the stage of fruit development and the species concerned. A tolerance index was developed to express the relative tolerance of macadamia cultivars to the damage caused by kernel-feeding Pentatomidae at the later stages of fruit development. Parameters for the index were the number of pentatomids attacking macadamia, their proboscis length and the combined thickness of the husk and shell of the fruit.

Effects of potassium on fruit soluble sugar and citrate accumulations in Cara Cara navel orange (Citrus sinensis L. Osbeck)

Sugars and organic acid are key factors for sensory properties of fruit quality. Potassium (K) is an essential macroelement and is also known as quality element. This study aims to investigate how K affects quality improvement particularly sucrose, fructose, glucose and citrate accumulations in Cara Cara navel orange. K fertilizer increased fruit sucrose, fructose, glucose and citrate concentrations and the ratios of total soluble sugars and citrate, particularly the ratios increased more in the treatment of 0.50 kg/plant K fertilizer. These results showed that suitable amount of K fertilizer could improve fruit quality of Cara Cara navel orange. Further study showed that, at early stage of fruit development, K fertilizer played more important roles in degrading sucrose due to the increased activities of sucrose-degrading enzymes including invertase and sucrose synthase-cleavage activity. Conversely, at late stage of fruit development, K fertilizer played more important roles in re-synthesizing sucrose due to the higher activities of sucrose-synthesizing enzymes including sucrose synthase-synthetic activity and sucrose phosphate synthase. The above results suggested that the upregulations of sucrose-degrading and sucrose-synthesizing enzyme activities caused by K fertilizer were conducive to improving sucrose metabolism and sink strength, and then increased the concentrations of sucrose, fructose and glucose in fruit. K fertilizer increased the activities of citrate-synthesizing enzymes including citrate synthetase and phosphoenolpyruvate carboxylase, but had no significant impacts on the activities of citrate-degrading enzyme, indicating that K fertilizer increased citrate accumulations at least partially by promoting its synthesis. This study finally suggested that K fertilizer improved the accumulations of soluble sugar and citrate in Cara Cara navel orange.