Different Stages Of Fruit Development Research Articles

Transcriptomic and metabolomic analyses reveal the importance of ethylene networks in mulberry fruit ripening

Mulberry (Morus alba L.) is a climacteric and highly perishable fruit. Ethylene has been considered to be an important trigger of fruit ripening process. However, the role of ethylene in the mulberry fruit ripening process remains unclear. In this study, we performed a comprehensive analysis of metabolomic and transcriptomic data of mulberry fruit and the physiological changes accompanying the fruit ripening process. Our study revealed that changes in the accumulation of specific metabolites at different stages of fruit development and ripening were closely correlated to transcriptional changes as well as underlying physiological changes and the development of taste biomolecules. The ripening of mulberry fruits was highly associated with the production of endogenous ethylene, and further application of exogenous ethylene assisted the ripening process. Transcriptomic analysis revealed that differential expression of diverse ripening-related genes was involved in sugar metabolism, anthocyanin biosynthesis, and cell wall modification pathways. Network analysis of transcriptomics and metabolomics data revealed that many transcription factors and ripening-related genes were involved, among which ethylene-responsive transcription factor 3 (MaERF3) plays a crucial role in the ripening process. The role of MaERF3 in ripening was experimentally proven in a transient overexpression assay in apples. Our study indicates that ethylene plays a vital role in modulating mulberry fruit ripening. The results provide a basis for guiding the genetic manipulation of mulberry fruits towards sustainable agricultural practices and improve post-harvest management, potentially enhancing the quality and shelf life of mulberry fruits for sustainable agriculture and forestry.

Evaluation of fruit detachment forces and related characteristics reveals differential fruit detachments at developmental stages and cultivar differences in cashew

Cashew is an edible tree nut with great nutritional and industrial importance. Cashew fruit is unique because the true fruit (nut) grows attached to a swollen flower pedicel known as a hypocarp or cashew apple. The fruit detachment force (FDF), a quantitative measurement of the detachment of fruits from the stalk, is considered as an important parameter for the evaluation of the harvesting efficiency of machines, and the cultivar's potential for machine harvesting, and tolerances to biotic and abiotic stresses. There have been no studies on the evaluation of FDFs in cashew to date. In the current study, we investigated the detachment forces of fruits at ten different stages of development according to the BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale, a uniform coding system for different growth or phenological stages (701, 703, 705, 707, 709, 811, 813, 815, 817, 819) in ten cashew cultivars. Fruit weight (FW), FDF/FW ratio, and fruit firmness (FF) for different fruit development stages and fruit stalk scar area (SSA) of matured (819 stage) fruits were also studied. FDF, FW, FDW/FW and FF varied significantly at the different stages of fruit development among the studied cultivars. The FDF increased from 701 to 709 stages and then decreased from 709 to 819 stages in all the studied cultivars. The FDW/FW ratio reduced with the development and maturity of the fruit. In matured fruits (811–819 stages), FW and FF showed significant negative (p value = 0.028) and positive (p value = 0.015.) correlations, respectively, with the FDF. In contrast, the SSA had no significant influence on the FDFs. As the FDF has direct implications on the fruit removal efficiency, the results of this study will be useful for designing harvesting machines, screening genotypes for stress tolerance, and identifying the optimal harvesting stage in cashew.

Genome-wide analysis of the bHLH family and identification of bHLH genes involved in fruit development and ripening of cultivated octoploid strawberry

Abstract Objectives The basic helix–loop–helix (bHLH) transcription factors (TFs) regulate fruit growth in many plants. However, there is no available study on the bHLH gene family in the haplotype-resolved genome of cultivated strawberry (Fragaria × ananassa). Materials and Methods The 131 FabHLH genes identified in the strawberry cultivar ‘Yanli’ haplotype-resolved genome were classified into 24 subfamilies according to their phylogenetic relationships. Gene structure, conserved motifs, and chromosomal locations were investigated using bioinformatics. Results In total, 15 FabHLH genes potentially involved in fruit development were screened based on transcriptome analysis of different stages of fruit development. We also identified the cis-regulatory elements of these 15 FabHLH genes, predicted upstream transcription factors, and identified protein–protein interactions. Conclusions The findings of this study improve our understanding of the regulation mediated by bHLH TFs during strawberry fruit growth and maturation.

Genome-Wide Identification and Analysis of the DGAT Gene Family in Lindera glauca and Expression Analysis during Fruit Development Stages

Diacylglycerol acyltransferase (DGAT) is a vital and sole rate-limiting enzyme involved in triacylglycerol synthesis. Identifying DGAT genes in Lindera glauca is essential for studying lipid metabolism pathways and developing novel oil crops with enhanced value. In the study reported in this paper, 15 LgDGAT family genes were first obtained from the L. glauca genome via bioinformatics analysis. We comprehensively analyzed their chromosome distribution, gene structure, subcellular localization, promoter prediction, phylogenetic relationships, tissue-specific expression, and expression patterns during different stages of fruit development. Our findings revealed that LgDGATs can be classified into DGAT1, DGAT2, DGAT3, and WSD (wax ester synthase/acyl-CoA: diacylglycerol acyltransferase) subfamilies distributed across chromosome 3, 5, 6, 8 and 11. LgDGATs’ promoter region showed abundant elements linked to the light response and plant hormone response. Forms of LgDGAT1, LgDGAT2, and LgDGAT3 were primarily expressed in the early and late phases of fruit development, indicating their potential function in the growth and development of L. glauca, particularly in oil accumulation. Conversely, LgWSDs exhibited predominant expression in stems and leaves. This paper elucidates the gene structure and expression patterns of LgDGATs, providing a theoretical foundation for understanding the functionality of DGAT genes in Lindera species.

Transcriptome Analysis Unveiled the Intricate Interplay between Sugar Metabolism and Lipid Biosynthesis in Symplocos paniculate Fruit.

Symplocos paniculate is an oil plant exhibiting tissue-specific variations in oil content and fatty acid composition across the whole fruit (mainly pulp and seed). And its oil synthesis is intricately linked to the accumulation and transformation of sugars. Nevertheless, there remains a dearth of understanding regarding how sugar metabolism impacts oil synthesis in S. paniculate fruit. To unravel the intricate mechanism underlying the impact of sugar metabolism on lipid biosynthesis in S. paniculata fruit, a comparative analysis was conducted on the transcriptome and metabolite content of pulp and seed throughout fruit development. The findings revealed that the impact of sugar metabolism on oil synthesis varied across different stages of fruit development. Notably, during the early fruit developmental stage (from 90 to 120 DAF), pivotal genes involved in sugar metabolism, such as PGK3, PKP1, PDH-E1, MDH, and malQ, along with key genes associated with oil synthesis like KAR, HAD, and PAP were predominantly expressed in the pulp. Consequently, this preferential expression led to earlier accumulation of oil in the pulp tissue compared to the seed. Whereas, during the fruit maturity stage (from 120 DAF to 140 DAF), these genes exhibited a high level of expression in seed, thereby facilitating the rapid and substantial accumulation of seed oil compared to pulp. The sugar metabolism activity in various parts of S. paniculata fruit plays a pivotal role in oil synthesis and is contingent upon the developmental stage. These findings can offer alternative genes for further gene enhancement through molecular biotechnology, thereby augmenting fruit oil yield and altering fatty acid composition.

Heat pulse velocity method for determining water requirements in rainfed sweet cherry trees (Prunus avium L.)

It is imperative to possess a comprehensive understanding of the water consumption patterns of sweet cherry trees under rainfed conditions. This study investigates the water use of sweet cherry using the heat pulse velocity sap flow method. Tree response to drying soil conditions over two consecutive measurement periods (September 2017 to December 2018) in the eastern Free State, South Africa, is also evaluated. During the post-harvest period (December), there was a continuous increase in daily water consumption by trees, in conjunction with an increase in canopy cover, even though the crop load was reduced. Measured sap flow was positively correlated to net radiation, air temperature, and water vapour pressure deficit. The transpiration rates ranged from 1.2 to 3.5 L d-1 during the flowering stage (day of year, DOY, 244 – 270) and showed an increasing trend as the days progressed. During the ripening stage (DOY 271 – 292), transpiration rates decreased from 4.5 to 1.1 L d-1 over the 2018 season. This decreasing trend from the previous growth stage was due to soil drying and scorching weather conditions that led to trees experiencing water stress. Sap flow measurements, however, showed typical characteristics of the diurnal trend during selected days during varying weather conditions. The fraction of transpirable soil water (FTSW) threshold varied for different fruit growth stages and approached 1.0 for different stress levels. FTSW exceeded 0.4 when sweet cherry trees utilised stored soil water, while the transpiration rates declined during prolonged hot days. Moreover, the stress coefficient factor ranged between 0.45 – 0.65 for different growth stages. The daily soil water content varied, and soil evaporation was expected to increase during hot and dry days. In the early stage of a dry spell, soil water content did not directly affect the transpiration rate. Sweet cherry trees are susceptible to soil water deficit at different stages of fruit development. More research is required to understand transpiration as an irrigation management and planning indicator.

X-RAY AND IMAGE ANALYSES OF SEEDS OF Passiflora cincinnata AND Passiflora morifolia

Wild species of passion fruit present characteristics such as resistance to diseases and pests, longevity, and adaptability to adverse climatic conditions. Morphological analyses of seeds of wild species are frequently performed to investigate reproductive aspects of plants used in genetic improvement programs. The present study evaluated the quality of seeds of Passiflora cincinnata and Passiflora morifolia at different stages of fruit development, through X-ray and GroundEye® software image analyses. Four repetitions of 50 seeds and four stages of fruit maturation were used. X-ray-exposed seeds were classified as "full" or "empty". The computerized image analysis evaluated 10 descriptors related to color dominance and 7 descriptors related to geometry. A germination test was subsequently performed. In X-rayed samples, a higher percentage of empty seeds was detected in the green phase of maturation (6% for P. cincinnata and 11% for P. morifolia). GroundEye software® findings indicated that differences in coloration may indicate differences in the physiological quality of seeds. The collective results indicate that fruits of P. cincinnata and P. morifolia can be collected at the "on time", mature, and senescent maturation stages without compromising the physiological quality.

Genome–Wide Investigation of the CBL–CIPK Gene Family in Oil Persimmon: Evolution, Function and Expression Analysis during Development and Stress

Ca2+-sensors, calcineurin B-like proteins (CBLs), and calcineurin B-like protein-interacting protein kinases (CIPKs) form a CBL–CIPK complex to regulate signal transduction. This study aimed to reveal the characteristics of the CBL–CIPK gene family in oil persimmon (Diospyros oleifera). Ten DoCBL and 23 DoCIPK genes were identified, and gene duplication among them was mainly attributed to segmental duplication. According to phylogenetic and structural analysis, DoCBLs were clustered into four groups with distinct motifs, namely myristoylation and palmytoylation sites in their N-terminus, and DoCIPKs containing a NAF/FISL domain were clustered into intron-rich and intron-less groups. The expression patterns of DoCBLs and DoCIPKs were tissue- and time-specific in different tissues and at different stages of fruit development. Most CBL–CIPK genes were upregulated under NaCl, drought, and Ca(NO3)2 stress using qRT-PCR analysis. DoCBL5 and DoCIPK05 were both located in the plasma membrane of cells using green fusion proteins (GFP) in tobacco leaves. DoCBL5 and DoCIPK05 might interact with AKT1, PP2C, and SNF to regulate the Ca2+ signals, K+, and ABA homeostasis in cells. In conclusion, these results suggested that the CBL–CIPK family genes might play important roles in oil persimmon growth and stress responses.

Genome-wide analysis of IQD proteins and ectopic expression of watermelon ClIQD24 in tomato suggests its important role in regulating fruit shape.

The plant-specific IQ67 domain (IQD) is the largest class of calmodulin targets found in plants, and plays an important role in many biological processes, especially fruit development processes. However, the functional role of IQD proteins in the development of watermelon (Citrullus lanatus) shape remains unknown, as the IQD protein family in watermelon has not been systematically characterized. Herein, we elucidated the gene structures, chromosomal locations, evolutionary divergence, and functions of 35 IQD genes in the watermelon genome. The transcript profiles and quantitative real-time PCR analysis at different stages of fruit development showed that the ClIQD24 gene was highly expressed on 0 days after pollination. Furthermore, we found that the ectopic overexpression of ClIQD24 promoted tomato fruit elongation, thereby revealing the significance of ClIQD24 in the progression of watermelon shape. Our study will serve as a reference for further investigations on the molecular mechanisms underlying watermelon fruit shape formation.

Identification and Characterization of the Tomato UGT Gene Family and Effects of GAME 17 Overexpression on Plants and Growth and Development under High-CO2 Conditions

Steroidal glycoalkaloids (SGAs), the nitrogen-containing compounds produced primarily by Liliaceae and Solanaceae species, are toxic to animals and humans and have putative roles in defense against pests. UDP-glycosyltransferases (UGTs) catalyze the final glycosylation steps of SGA biosynthesis. Although previously published studies focused on the effect of UGT proteins on SGA biosynthesis, research to understand the effects of constitutive overexpression of UGTs on plant phenotype and fruit development is limited. The constitutive overexpression of a UGT encoding gene, GAME 17, may provide an alternative method to study the role of UGTs on the fruit development. In this study, we have identified 162 SlUGT proteins in tomato that are classified into t 23 groups. Gene structure and motif analyses have demonstrated that all SlUGTs have similar intron/exon distribution and motif compositions. RNA-seq data analysis has shown that SlUGTs exhibit differential expression patterns in different organs or different stages of fruit development. When the constitutive promoter 35S is used to control the expression of GAME 17, we have observed significant differences in growth parameters (i.e., plant height, leaf length, leaf width, internode length, and stem diameter) between WT and transgenic plants under high-CO2 conditions, and slight differences in growth parameters between WT and transgenic plants have beendetected. In addition, the contents of glucose, fructose, and soluble sugar of transgenic plants are significantly higher than those of WT plants. The increases in glucose, fructose, and soluble sugar in transgenic tomato fruits at three developmental stages under high-CO2 conditions are significantly higher than under natural conditions. This study provides additional evidence that the GAME 17 gene plays an important role in controlling plant phenotype and sugar homeostasis, especially in environments with high concentration of CO2.

The metaxenia effects of different pollen grains on secondary metabolites enzymes and sugars of ‘Piarom’ date palm fruit

In this research, the characteristics of pollen were studied in eight pollinating cultivars of date palm, namely, ‘Shahani’, ‘Kabkab’, ‘Zahedi’, ‘Beraem’, ‘Faryab’, ‘Sheikhali’, ‘Fard’ and ‘Jarvis’. The characteristics were compared and metaxenia effects were evaluated on secondary metabolites, enzymes and other biochemical compounds of ‘Piarom’ date fruits. The evaluations were carried out during four stages of fruit growth and development. The pollen of these eight pollinating cultivars were compared in terms of carbohydrates, proteins, starch, total phenol, flavonoids, pectin methyl esterase, and amylase enzymes. According to the results, the pollen of ‘Sheikhali’, ‘Fard’, ‘Zahedi’ and ‘Shahani’ cultivars contained more of the above compounds, compared to the other cultivars. Regarding the effects of pollen on the composition of ‘Piarom’ date fruits, ‘Fard’ and ‘Sheikhali’ pollen produced the lowest amount of soluble tannin, which resulted in a better quality of ‘Piarom’ date fruits. Pollen was also obtained from ‘Sheikhali’ and ‘Fard’ cultivars for evaluations, showing that they led to the highest amounts of glucose and fructose in the fruits. Regarding the sucrose amount, ‘Jarvis’ and ‘Shikhali’ produced the best results. Pollen of ‘Sheikhali’ and ‘Fard’ cultivars caused the lowest amount of chlorophyll at the different stages of fruit growth, indicating a better decomposition of fruit chlorophyll and, as a result, better fruit quality. Pollen of ‘Sheikhali’ and ‘Fard’ cultivars produced the highest amounts of secondary metabolites such as total phenol, carotenoids and anthocyanin at the different stages of fruit development. The pollen of ‘Fard’ and ‘Sheikhali’ cultivars produced the highest levels of polygalacturonase, cellulase and invertase enzymes at different growth stages of the ‘Piarom’ date fruit. Regarding cellulase enzyme, fruits of the ‘Zahedi’ cultivar had more cellulase than the fruits of ‘Sheikhali’. In general, the pollen of ‘Fard’ and ‘Sheikhali, in comparison with other cultivars, improved the quantity and quality of ‘Piarom’ date fruits, due to their metaxenia properties.

Reduced auxin signalling through the cyclophilin gene DIAGEOTROPICA impacts tomato fruit development and metabolism during ripening.

Auxin is an important hormone playing crucial roles during fruit growth and ripening; however, the metabolic impact of changes in auxin signalling during tomato (Solanum lycopersicum L.) ripening remains unclear. Here, we investigated the significance of changes in auxin signalling during different stages of fruit development by analysing changes in tomato fruit quality and primary metabolism using mutants with either lower or higher auxin sensitivity [diageotropica (dgt) and entire mutants, respectively]. Altered auxin sensitivity modifies metabolism, through direct impacts on fruit respiration and fruit growth. We verified that the dgt mutant plants exhibit reductions in fruit set, total fruit dry weight, fruit size, number of seeds per fruit, and fresh weight loss during post-harvest. Sugar accumulation was associated with delayed fruit ripening in dgt, probably connected with reduced ethylene levels and respiration, coupled with a lower rate of starch degradation. In contrast, despite exhibiting parthenocarpy, increased auxin perception (entire) did not alter fruit ripening, leading to only minor changes in primary metabolism. By performing a comprehensive analysis, our results connect auxin signalling and metabolic changes during tomato fruit development, indicating that reduced auxin signalling led to extensive changes in sugar concentration and starch metabolism during tomato fruit ripening.

Metabolomic Profiling of Citrus unshiu during Different Stages of Fruit Development.

Citrus fruits undergo significant metabolic profile changes during their development process. However, limited information is available on the changes in the metabolites of Citrus unshiu during fruit development. Here, we analyzed the total phenolic content (TPC), total carotenoid content (TCC), antioxidant activity, and metabolite profiles in C. unshiu fruit flesh during different stages of fruit development and evaluated their correlations. The TPC and antioxidant activity significantly decreased during fruit development, whereas the TCC increased. The metabolite profiles, including sugars, acidic compounds, amino acids, flavonoids, limonoids, carotenoids, and volatile compounds (mono- and sesquiterpenes), in C. unshiu fruit flesh also changed significantly, and a citrus metabolomic pathway related to fruit development was proposed. Based on the data, C. unshiu fruit development was classified into three groups: Group 1 (Aug. 1), Group 2 (Aug. 31 and Sep. 14), and Group 3 (Oct. 15 and Nov. 16). Although citrus peel was not analyzed and the sensory and functional qualities during fruit development were not investigated, the results of this study will help in our understanding of the changes in chemical profile during citrus fruit development. This can provide vital information for various applications in the C. unshiu industry.

Genome-Wide Identification and Bioinformatics Analysis of Auxin Response Factor Genes in Highbush Blueberry

Auxin response factors (ARFs) are a transcription factor family that regulates the expression of auxin phase-responsive genes. Here, we performed a genome-wide investigation of the tetraploid blueberry (Vaccinium corymbosum cv. ‘Draper’) genome sequence. Physical and chemical properties, phylogenetic evolution, gene structure, conservative motifs, chromosome location, and cis-acting elements of blueberry ARF genes were comprehensively evaluated. A total of 70 blueberry ARF genes (VcARF) were found in its genome, which could be divided into six subfamilies. VcARF genes were unevenly distributed on 40 chromosomes and were observed to encode protein sequences ranging in length from 162 to 1117 amino acids. Their exon numbers range from 2 to 22. VcARF promoter regions contain multiple functional domains associated with light signaling, aerobic metabolism, plant hormones, stress, and cell cycle regulation. More family members of VcARF genes were discovered in blueberry than in previously studied plants, likely because of the occurrence of whole-genome duplication and/or tandem duplication. VcARF expression patterns were analyzed at different stages of fruit development, and VcARF3, VcARF4, VcARF14, VcARF37, and VcARF52 were observed to play important roles. VcARF3 and VcARF4 appeared to function as repressors, while VcARF14 acted as an essential factor in fruit firmness differences between firm and soft flesh cultivars.

Continuous Monitoring of Olive Fruit Growth by Automatic Extensimeter in Response to Vapor Pressure Deficit from Pit Hardening to Harvest

Recently, several studies on olive fruit growth have focused on circadian monitoring as an important orchard management tool. The olive fruit growth trend is described by double sigmoid model with four growth phases, where the third phase spans from the end of pit hardening to initial fruit maturation, and the last phase includes olive maturation up to fruit drop. Environmental factors play an important role in fruit growth, with vapor pressure deficit (VPD) being a keystone factor. Our experiment was designed to hourly monitor olive (Olea europaea L. cv. ‘Frantoio’) fruit transversal diameter from approximately initial pit hardening (II Phase), extension (III Phase) until harvest time (IV Phase) in the attempt to determine whether fruit growth dynamically responds to environmental variables such as diurnal VPD change in different stages of fruit development. Automatic extensimeters were applied in open field and VPD was calculated from data of our weather station. Throughout the experiment period, the circadian model of fruit growth showed two steps: shrinkage and expansion. Almost in all days of the third phase of fruit growth, daily response of transversal diameter to VPD formed complete clockwise hysteresis loops. During the fourth phase of fruit growth, with increasing fruit maturation, the complete clockwise hysteresis loop experienced some abnormality. At the fourth stage of fruit growth there were incomplete and partial clockwise hysteresis loops. We conclude that hysteresis can be employed to detect the shift between the end of the third phase (cell expansion) and the beginning of the fourth phase (fruit maturation) of fruit growth. The disappearance of the complete clockwise hysteresis loop and the substitution with incomplete, or partial clockwise hysteresis loops was observable only in the fourth stage of fruit growth. These results can be valuable for any smart fruit management of olive fruit production.

MicroRNA Profiling During Mulberry (Morus atropurpurea Roxb) Fruit Development and Regulatory Pathway of miR477 for Anthocyanin Accumulation.

To understand the mechanism of small non-coding RNAs (miRNA)-mediated development and ripening of mulberry fruits, three small RNA libraries from mulberry fruits at different development stages were constructed, and 159 conserved miRNAs as well as 86 novel miRNAs were successfully identified. Among the miRNAs identified, there were 90 miRNAs which showed differential expression patterns at different stages of fruit development and ripening. The target genes of these differential expressed (DE) miRNAs were involved in growth and development, transcription and regulation of transcription, metabolic processes, and etc. Interestingly, it was found that the expression level of mul-miR477 was increased with fruit ripening, and it can target the antisense lncRNA (Mul-ABCB19AS) of the ATP binding cassette (ABC) transporter B 19 gene (Mul-ABCB19). Our results showed that mul-miR477 can repress the expression of Mul-ABCB19AS and increase the expression of Mul-ABCB19, and it acted as a positive regulator participating anthocyanin accumulation through the regulatory network of mul-miR477—Mul-ABCB19AS—Mul-ABCB19.

A Transcriptional Analysis of the Genes Involved in the Ascorbic Acid Pathways Based on a Comparison of the Juice and Leaves of Navel and Anthocyanin-Rich Sweet Orange Varieties.

Sweet oranges are an important source of ascorbic acid (AsA). In this study, the content of AsA in the juice and leaves of four orange clonal selections, different in terms of maturity time and the presence/absence of anthocyanins, was correlated with the transcription levels of the main genes involved in the biosynthesis, recycling, and degradation pathways. Within each variety, differences in the above pathways and the AsA amount were found between the analysed tissues. Variations were also observed at different stages of fruit development and maturation. At the beginning of fruit development, AsA accumulation was attributable to the synergic action of l-galactose and Myo-inositol, while the l-gulose pathway was predominant between the end of fruit development and the beginning of ripening. In leaves, the l-galactose pathway appeared to play a major role in AsA accumulation, even though higher GalUr isoform expression suggests a synergistic contribution of both pathways in this tissue. In juice, the trend of the AsA content may be related to the decrease in the transcription levels of the GME, GDH, MyoOx, and GalUr12 genes. Newhall was the genotype that accumulated the most AsA. The difference between Newhall and the other varieties seems to be attributable to the GLDH, GalUr12, APX2, and DHAR3 genes.

The transcriptional landscape of cultivated strawberry (Fragaria×ananassa) and its diploid ancestor (Fragaria vesca) during fruit development

Cultivated strawberry (Fragaria×ananassa) originated from four diploid ancestors: F. vesca, F. viridis, F. iinumae and F. nipponica. Among them, F. vesca is the dominant subgenome for cultivated strawberry. It is not well understood how differences in gene expression between diploid and octoploid strawberry contribute to differences during fruit development. In this study, we used comprehensive transcriptomic analyses of F. vesca and F.×ananassa to investigate gene expression at the different stages of fruit development. In total, we obtained 3 508 (turning stage) and 3 958 (red stage) differentially expressed genes with pairwise comparisons between diploid and octoploid. The genes involved in flavonoid biosynthesis were almost upregulated in the turning stages of octoploid, and we also discovered a ripe fruit-specific module associated with several flavonoid biosynthetic genes, including FveMYB10, FveMYB9/11, and FveRAP, using weighted gene coexpression network analysis (WGCNA). Furthermore, we identified the species-specific regulated networks in the octoploid and diploid fruit. Notably, we found that the WAK and F-box genes were enriched in the octoploid and diploid fruits, respectively. This study elucidates new findings on flavonoid biosynthesis and fruit size of strawberry with important implications for future molecular breeding in cultivated strawberry.

Variation in the content and composition of limonoids in fruits of four pomelo varieties during fruit development: The natural debittering process in pomelo fruits

Bitterness, which is mainly attributed to limonoids, seriously affects the taste of pomelo fruits and hinders their competitiveness in the market. Therefore, a high-performance liquid chromatography method was developed for simultaneous isolation and determination of limonin, nomilin, and limonin glucoside contents in pomelo fruit, and the method showed good precision (RSD ≤ 2.85 %), repeatability (RSD ≤ 3.37 %) and high sample recovery rate (95.8 %–99.7 %). Four pomelo varieties were used to investigate the accumulation and distribution of limonoids in different stages of fruit development and in different plant tissues and varieties, as well as to reveal the synthesis mechanism and provide a basis for the utilisation of pomelo resources in different industries. Results showed that flavedo was the tissue richest in limonoids, and the maximum limonoid content could reach 5959 μg/g fresh weight. During fruit growth and development, the limonin and nomilin contents in juice sacs and albedo first increased and then decreased. Although there were some fluctuations, the limonin and nomilin contents in the flavedo generally showed a decreasing trend with fruit development. Our investigation of the LGT gene expression pattern provided the basis for exploring natural debittering mechanisms in pomelo. Expression of the LGT gene was positively correlated with limonin glucoside content.

The pineapple MADS-box gene family and the evolution of early monocot flower

Unlike the flower of the model monocot rice, which has diverged greatly from the ancestral monocot flower, the pineapple (Ananas comosus) flower is more typical of monocot flowers. Here, we identified 43 pineapple genes containing MADS-box domains, including 11 type I and 32 type II genes. RNA-seq expression data generated from five pineapple floral organs (sepals, petals, stamens, pistils, and ovules) and quantitative real-time PCR revealed tissue-specific expression patterns for some genes. We found that AcAGL6 and AcFUL1 were mainly expressed in sepals and petals, suggesting their involvement in the regulation of these floral organs. A pineapple ‘ABCDE’ model was proposed based on the phylogenetic analysis and expression patterns of MADS-box genes. Unlike rice and orchid with frequent species-specific gene duplication and subsequent expression divergence, the composition and expression of the ABCDE genes were conserved in pineapple. We also found that AcSEP1/3, AcAG, AcAGL11a/b/c, and AcFUL1 were highly expressed at different stages of fruit development and have similar expression profiles, implicating these genes’ role in fruit development and ripening processes. We propose that the pineapple flower can be used as a model for studying the ancestral form of monocot flowers to investigate their development and evolutionary history.