Comparative analysis of the difference in flavonoid metabolic pathway during coloring between red-yellow and red sweet cherry (Prunus avium L.)

The color of a fruit is an important contributor to the perception of its nutritional value. It is widely acknowledged that the color of sweet cherry changes obviously during ripening. Variations in anthocyanins and flavonoids account for the heterogeneous color of sweet cherries. In this study, we showed that anthocyanins but not carotenoids determine the color of sweet cherry fruits. The difference between red-yellow and red sweet cherry may be attributed to seven anthocyanins, including Cyanidin-3-O-arabinoside, Cyanidin-3,5-O-diglucoside, Cyanidin 3-xyloside, Peonidin-3-O-glucoside, Peonidin-3-O-rutinoside, Cyanidin-3-O-galactoside, Cyanidin-3-O-glucoside (Kuromanin), Peonidin-3-O-rutinoside-5-O-glucoside, Pelargonidin-3-O-glucoside and Pelargonidin-3-O-rutinoside. The content of 85 flavonols differed between red and red-yellow sweet cherries. The transcriptional analysis identified 15 key structural genes involved in the flavonoid metabolic pathway and four R2R3-MYB transcription factors. The expression level of Pac4CL, PacPAL, PacCHS1, PacCHS2, PacCHI, PacF3H1, PacF3H2, PacF3'H, PacDFR, PacANS1, PacANS2, PacBZ1 and four R2R3-MYB were positively correlated with anthocyanin content (ps < 0.05). PacFLS1, PacFLS2 and PacFLS3 expression was negatively correlated with anthocyanin content but positively correlated with flavonols content (ps < 0.05). Overall, our findings suggests that the heterogeneous expression of structural genes in the flavonoid metabolic pathway accounts for the variation in levels of final metabolites, leading to differences between red 'Red-Light' and red-yellow 'Bright Pearl'.

Beyond green and red: unlocking the genetic orchestration of tomato fruit color and pigmentation

Fruit color is a genetic trait and a key factor for consumer acceptability and is therefore receiving increasing importance in several breeding programs. Plant pigments offer plants with a variety of colored organs that attract animals for pollination, favoring seed dispersers and conservation of species. The pigments inside plant cells not only play a light-harvesting role but also provide protection against light damage and exhibit nutritional and ecological value for health and visual pleasure in humans. Tomato (Solanum lycopersicum) is a leading vegetable crop; its fruit color formation is associated with the accumulation of several natural pigments, which include carotenoids in the pericarp, flavonoids in the peel, as well as the breakdown of chlorophyll during fruit ripening. To improve tomato fruit quality, several techniques, such as genetic engineering and genome editing, have been used to alter fruit color and regulate the accumulation of secondary metabolites in related pathways. Recently, clustered regularly interspaced short palindromic repeat (CRISPR)-based systems have been extensively used for genome editing in many crops, including tomatoes, and promising results have been achieved using modified CRISPR systems, including CAS9 (CRISPR/CRISPR-associated-protein) and CRISPR/Cas12a systems. These advanced tools in biotechnology and whole genome sequencing of various tomato species will certainly advance the breeding of tomato fruit color with a high degree of precision. Here, we attempt to summarize the current advancement and effective application of genetic engineering techniques that provide further flexibility for fruit color formation. Furthermore, we have also discussed the challenges and opportunities of genetic engineering and genome editing to improve tomato fruit color.

Targeting ripening regulators to develop fruit with high quality and extended shelf life

Fruit quality directly impacts fruit marketability and consumer acceptance. Breeders have focused on fruit quality traits to extend shelf life, primarily through fruit texture, but, in some cases, have neglected other qualities such as flavor and nutrition. In recent years, integrative biotechnology and consumer-minded approaches have surfaced, aiding in the development of flavorful, long-lasting fruit. Here, we discussed how specific transcription factors and hormones involved in fruit ripening can be targeted to generate high-quality fruit through traditional breeding and bioengineering. We highlight regulators that can be used to generate novel-colored fruit or biofortify fresh produce with health-promoting nutrients, such as vitamin C. Overall, we argue that addressing grower and industry needs must be balanced with consumer-based traits.

Transcriptome and metabolome analyses reveal anthocyanins pathways associated with fruit color changes in plum (Prunus salicina Lindl.)

Plum (Prunus salicina Lindl.) is one of the most widely cultivated and important fruit trees in temperate and cold regions. Fruit color is a significant trait relating to fruit quality in plum. However, its development mechanism has not been studied from the aspects of transcriptional regulation and metabolomic progress. To reveal the mechanism of fruit color developments in plums, we selected the fruits of two plum cultivars, 'Changli84' (Ch84, red fruit) and 'Dahuangganhe' (D, yellow fruit) as plant materials for transcriptome sequencing and metabolomic analysis were performed. Based on the data of transcriptome and metabolome at three fruit developmental stages, young fruit stage, color-change stage, and maturation stage, we identified 2,492 differentially expressed genes (DEGs) and 54 differential metabolites (DMs). The KEGG analysis indicated that "Flavonoid biosynthesis" was significantly enriched during three fruit development stages. Some DEGs in the "Flavonoid biosynthesis" pathway, had opposite trends between Ch84 and D, including chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR) and flavonol synthase (FLS). Also, the genes encoding MYB-bHLH-WD (MBW) protein complexes, especially MYBs and bHLHs, showed a close relationship with plum fruit color. In the current study, DMs like procyanidin B1, cyanidin 3-glucoside, and cyanidin-3-O-alpha-arabinopyranoside were key pigments (or precursors), while the carotene and carotenoids did not show key relationships with fruit color. In conclusion, the anthocyanins dominate the color change of plum fruit. Carotenes and carotenoids might be related to the color of plum fruit, but do not play a dominate role.

Comparative transcriptomic analysis identifies KcMYB1 as a R2R3-MYB anthocyanin activator in Kadsura coccinea

Fruit color, as an important appearance attribute, is crucial for attracting consumers. However, the underlying mechanism regulating mature fruit color formation in Kadsura coccinea remains unclear. Here, a comprehensive metabolomics and transcriptomics analysis was performed to investigate the molecular mechanisms of anthocyanin accumulation between two K. coccinea cultivars with different mature fruit colors-'Dahong No. 1' (red) and 'Jinhu' (yellow). Targeted metabolomic analysis revealed high anthocyanin levels, most of which were cyanidin and delphinidin derivatives, in 'Dahong No. 1' mature fruit peel. The SNP analysis indicated that the two different cultivars had similar genetic background. Moreover, comparative transcriptomic analysis demonstrated that differentially expressed genes (DEGs) were related to flavonoid biosynthesis and metabolic process in the two K. coccinea cultivars. Gene expression profiling data showed that the structural and regulatory genes associated with anthocyanin biosynthesis were significantly upregulated in 'Dahong No. 1' mature fruit peel, which was verified by quantitative real-time polymerase chain reaction (qRT-PCR). Notably, the key anthocyanin activator KcMYB1 was identified, which was significantly upregulated in 'Dahong No. 1' compared with 'Jinhu'. We further confirmed that KcMYB1 actively regulated the accumulation of anthocyanin by ectopic expression in vivo. Furthermore, allelic constitution of KcMYB1 in K. coccinea were investigated. The present study can provide insights for understanding the regulatory mechanisms of anthocyanin differential accumulation in the mature fruits of K. coccinea.

Functional R2R3-MYB transcription factor NsMYB1, regulating anthocyanin biosynthesis, was relative to the fruit color differentiation in Nitraria sibirica Pall

BACKGROUND

Nitraria sibirica Pall. is an economic plant with two kinds of fruit color, widely spreads in the Qinghai Tibet Plateau. The chemical analysis and pharmacological evaluation had been carried out for several tens of years, the mechanism behind the fruit color differentiation is still unclear.

RESULTS

In this manuscript, the chemical analysis of the extractions showed that the chemical composition of fruit color was anthocyanin, and two kind of Nitraria sibirica Pall. were caused by the content differentiation with the same anthocyanin kinds. Cyanidin-3-[2"-(6'"-coumaroyl)-glucosyl]-glucoside (C3G) was the major anthocyanin. Transcriptome analysis and the qRT-PCR revealed that the structural genes relative to anthocyanin biosynthesis except CHS, F3'5'H and ANS were up-regulated in the peels of BF (Black fruit) compared with the peels of RF (Red fruit), which indicated that transcript factor should be the reason for the expression difference of the structure genes. In the unigenes of the transcript factor MYB and bHLH, relative to anthocyanin, only NsMYB1 (Cluster 8422.10600), was high-expression and up-expression in the peels of BF. NsMYB1 encoded the same length protein with four amino acid differences in the RF and BF, and both contained the intact DNA, HTH-MYB and SANT domains. NsMYB1 was close to the AtMYB114, AtMYB113 and AtPAP1, regulating anthocyanin biosynthesis, in phylogenetic relationship. Both NsMYB1r and NsMYB1b could promote the transcript of the structural genes, and induced the anthocyanin accumulation in all tissues of transgenic tobacco. The insertion of 'TATA' in the promoter of NsMYB1r gave one more promoter region, and was the reason for higher transcripts in black fruit possibly.

CONCLUSIONS

Cyanidin-3-[2''-(6'"-coumaroyl)-glucosyl]-glucoside was the major anthocyanin in black fruit of Nitraria sibirica Pall.. NsMYB1 was a functional R2R3-MYB transcription factor, regulated the anthocyanin biosynthesis, and led to the fruit color differentiation in Nitraria sibirica Pall.

Light regulation of potassium in plants

Essential macronutrient potassium (K) and environmental signal light regulate a number of vital plant biological processes related to growth, development, and stress response. Recent research has shown connections between the perception of light and the regulation of K in plants. Photoreceptors-mediated wavelength-specific light perception activates signaling cascades which mediate stomatal movement by altering K⁺influx/efflux via K⁺ channels in the guard cells. The quality, intensity, and duration of light affect the regulation of K nutrition and crop quality. Blue/red illumination or red combined blue light treatment increases the expression levels of K transporter genes, K uptake and accumulation, leading to increased lycopene synthesis and improved fruit color in tomato. Despite the commonalities of light and K in multiple functions, our understanding of light regulation of K and associated physiological and molecular processes is fragmentary. In this review, we take a look at the light-controlled K uptake and utilization in plants and propose working models to show potential mechanisms. We discuss major light signaling components, their possible involvement in K nutrition, stomatal movement and crop quality by linking the perception of light signal and subsequent regulation of K. We also pose some outstanding questions to guide future research. Our analysis suggests that the enhancement of K utilization efficiency by manipulation of light quality and light signaling components can be a promising strategy for K management in crop production.

Molecular research progress and improvement approach of fruit quality traits in cucumber

Recent molecular studies revealed new opportunities to improve cucumber fruit quality. However, the fruit color and spine traits molecular basis remain vague despite the vast sources of genetic diversity. Cucumber is agriculturally, economically and nutritionally important vegetable crop. China produces three-fourths of the world's total cucumber production. Cucumber fruit quality depends on a number of traits such as the fruit color (peel and flesh color), spine (density, size and color), fruit shape, fruit size, defects, texture, firmness, taste, maturity stage and nutritional composition. Fruit color and spine traits determine critical quality attributes and have been the interest of researchers at the molecular level. Evaluating the molecular mechanisms of fruit quality traits is important to improve production and quality of cucumber varieties. Genes and qualitative trait locus (QTL) that are responsible for cucumber fruit color and fruit spine have been identified. The purpose of this paper is to reveal the molecular research progress of fruit color and spines as key quality traits of cucumber. The markers and genes identified so far could help for marker-assisted selection of the fruit color and spine trait in cucumber breeding and its associated nutritional improvement. Based on the previous studies, peel color and spine density as examples, we proposed a comprehensive approach for cucumber fruit quality traits improvement. Moreover, the markers and genes can be useful to facilitate cloning-mediated genetic breeding in cucumber. However, in the era of climate change, increased human population and high-quality demand of consumers, studies on molecular mechanisms of cucumber fruit quality traits are limited.

Research progress of fruit color development in apple (Malus domestica Borkh.)

Apple (Malus domestica Borkh.) is one of the most widely produced and economically important fruits in temperate regions. Fruit color development in apple is a major focus for both breeders and researchers as consumers associate brightly colored red apples with ripeness and a good flavor. In recent years, great progress has been made in the research of apple fruit color development, but its development mechanism has not been systematic dissected from the aspects of genetics, transcription or environmental factors. Here, we summarize research on the coloration of apple fruit, including the development of important genomic databases to identify important genomic regions and genes, genetic and transcriptional factors that regulate pigment accumulation, environmental factors that affect anthocyanin synthesis, and the current breeding progress of red-skinned and red-fleshed apples. We describe key transcription factors, such as MYB, bHLH, and WD40, which are involved in the regulation of anthocyanin synthesis and fruit color development in apple. We also discuss the regulation of apple color by external environmental factors such as light, temperature, and water. The aim of this review is to provide insights into the molecular mechanisms underlying anthocyanin biosynthesis in apple. This information will provide significant guidance for the breeding of high-quality red-skinned and red-fleshed apple varieties.

Integrative analysis of metabolome and transcriptome reveals the mechanism of color formation in pepper fruit (Capsicum annuum L.)

To understand the mechanism of the color formation of pepper fruit, integrative analysis of the metabolome and transcriptome profiles was performed in pepper varieties with 4 different fruit colors. A total of 188 flavonoids were identified, and most of the anthocyanins, flavonols and flavones showed markedly higher abundances in purple variety than in other varieties, which was linked to the high expression of flavonoid synthesis and regulatory genes. Using weighted gene co-expression network analyses, modules related to flavonoid synthesis and candidate genes that regulate flavonoid synthesis and transport were identified. Furthermore, the analysis of 12 carotenoids showed that the content of xanthophylls at 50 days after anthesis was significantly different between the four pepper varieties, which was resulted from the differential expressions of genes downstream of the carotenoid pathway. Our results provide new insights into the understanding of the synthesis and accumulation of flavonoids and carotenoids in pepper fruit.

Fruit syndromes in Viburnum: correlated evolution of color, nutritional content, and morphology in bird-dispersed fleshy fruits

PREMISE

A key question in plant dispersal via animal vectors is where and why fruit colors vary between species and how color relates to other fruit traits. To better understand the factors shaping the evolution of fruit color diversity, we tested for the existence of syndromes of traits (color, morphology, and nutrition) in the fruits of Viburnum. We placed these results in a larger phylogenetic context and reconstructed ancestral states to assess how Viburnum fruit traits have evolved across the clade.

RESULTS

We find that blue Viburnum fruits are not very juicy, and have high lipid content and large, round endocarps surrounded by a small quantity of pulp. Red fruits display the opposite suite of traits: they are very juicy with low lipid content and smaller, flatter endocarps. The ancestral Viburnum fruit may have gone through a sequence of color changes before maturation (green to yellow to red to black), though our reconstructions are equivocal. In one major clade of Viburnum (Nectarotinus), fruits mature synchronously with reduced intermediate color stages. Most transitions between fruit colors occurred in this synchronously fruiting clade.

CONCLUSIONS

It is widely accepted that fruit trait diversity has primarily been driven by the differing perceptual abilities of bird versus mammal frugivores. Yet within a clade of largely bird-dispersed fruits, we find clear correlations between color, morphology, and nutrition. These correlations are likely driven by a shift from sequential to synchronous development, followed by diversification in color, nutrition, and morphology. A deeper understanding of fruit evolution within clades will elucidate the degree to which such syndromes structure extant fruit diversity.

Integrative analysis of metabolome and transcriptome reveals the mechanism of color formation in pepper fruit (Capsicum annuum L.)

To understand the mechanism of the color formation of pepper fruit, integrative analysis of the metabolome and transcriptome profiles was performed in pepper varieties with 4 different fruit colors. A total of 188 flavonoids were identified, and most of the anthocyanins, flavonols and flavones showed markedly higher abundances in purple variety than in other varieties, which was linked to the high expression of flavonoid synthesis and regulatory genes. Using weighted gene co-expression network analyses, modules related to flavonoid synthesis and candidate genes that regulate flavonoid synthesis and transport were identified. Furthermore, the analysis of 12 carotenoids showed that the content of xanthophylls at 50 days after anthesis was significantly different between the four pepper varieties, which was resulted from the differential expressions of genes downstream of the carotenoid pathway. Our results provide new insights into the understanding of the synthesis and accumulation of flavonoids and carotenoids in pepper fruit.

Functional MYB transcription factor encoding gene AN2 is associated with anthocyanin biosynthesis in Lycium ruthenicum Murray

BACKGROUND

Lycium ruthenicum Murray is an important economic plant in China and contains higher levels of anthocyanins in its fruits than other Lyciums. However, the genetic mechanism of anthocyanin production in this plant is unknown.

RESULTS

Based on previous transcriptome analysis, LrAN2 and LbAN2, encoding MYB transcription factors, were isolated from L. ruthenicum and L. barbarum, respectively. Both genes contained two introns, encoded 257 amino acids with two-Aa difference, and carried the unabridged HTH-MYB, MYB-like DNA-binding, and SANT domains. In the phylogenetic trees, LrAN2 and LbAN2 were found to be closely related to NtAN2, which regulates anthocyanin biosynthesis in tobacco. Overexpression of LrAN2 and LbAN2 induced anthocyanin biosynthesis in all tissues of tobacco. The anthocyanin content in the leaves of transgenic lines with LbAN2 was lower than LrAN2. It indicated that the function of LbAN2 was weaker than LrAN2. The AN2 transcript could be detected only in the fruits of L. ruthenicum and increased during fruit development, accompanied by anthocyanin accumulation. In natural population, the alleles LrAN2 and LrAN2 were associated strictly with L. ruthenicum and L. barbarum, respectively. Moreover, an AN2 genetic diversity study suggested that Lyciums with yellow, white, purple, and jujube red fruits were derived from L. ruthenicum.

CONCLUSIONS

Two AN2 alleles, from L. ruthenicum and L. barbarum, were functional MYB transcriptor regulating anthocyanin biosynthesis. The functional diversity and high expression level of LrAN2 could be the reason for high anthocyanin content in the fruit of L. ruthenicum. Lyciums with yellow, white, purple, and jujube red fruits were derived from L. ruthenicum based on AN2 sequence diversity. The results may be advantageous in identifying new varieties and breeding new cultivars.

Genome wide identification and predicted functional analyses of NAC transcription factors in Asian pears

BACKGROUND

NAC proteins contribute to diverse plant developmental processes as well as tolerances to biotic and abiotic stresses. The pear genome had been decoded and provided the basis for the genome-wide analysis to find the evolution, duplication, gene structures and predicted functions of PpNAC transcription factors.

RESULTS

A total of 185 PpNAC genes were found in pear, of which 148 were mapped on chromosomes while 37 were on unanchored scaffolds. Phylogeny split the NAC genes into 6 clades (Group1- Group6) with their sub clades (~ subgroup A to subgroup H) and each group displayed common motifs with no/minor change. The numbers of exons in each group varied from 1 to 12 with an average of 3 while 44 pairs from all groups showed their duplication events. qPCR and RNA-Seq data analyses in different pear cultivars/species revealed some predicted functions of PpNAC genes i.e. PpNACs 37, 61, 70 (2A), 53, 151(2D), 10, 92, 130 and 154 (3D) were potentially involved in bud endodormancy, PpNACs 61, 70 (2A), 172, 176 and 23 (4E) were associated with fruit pigmentations in blue light, PpNACs 127 (1E), 46 (1G) and 56 (5A) might be related to early, middle and late fruit developments respectively. Besides, all genes from subgroups 2D and 3D were found to be related with abiotic stress (cold, salt and drought) tolerances by targeting the stress responsive genes in pear.

CONCLUSIONS

The present genome-wide analysis provided valuable information for understanding the classification, motif and gene structure, evolution and predicted functions of NAC gene family in pear as well as in higher plants. NAC TFs play diverse and multifunctional roles in biotic and abiotic stresses, growth and development and fruit ripening and pigmentation through multiple pathways in pear.

Anthocyanin biosynthesis is differentially regulated by light in the skin and flesh of white-fleshed and teinturier grape berries

Light exclusion reduces the concentration and modifies the composition of grape anthocyanins, by altering the expression of genes involved in anthocyanin biosynthesis and transport, in a cultivar- and tissue-specific manner. Unlike most grapes, teinturier grapes accumulate anthocyanins both in skin and flesh. However, the concentration and composition of anthocyanins in both tissues differ, providing a valuable system to study tissue-specific regulation of anthocyanin synthesis. Furthermore, little is known about the mechanisms controlling the sensitivity of anthocyanin accumulation to light. Here, light was excluded from Gamay (white-fleshed) and Gamay Fréaux (teinturier mutant) berries throughout berry development. Under light-exposed conditions, the skin of Gamay Fréaux accumulated the highest level of anthocyanins, followed by the skin of Gamay, while the pulp of Gamay Fréaux had much lower anthocyanins than the skins. Network analysis revealed the same order on the number of significant correlations among metabolites and transcripts in the three colored tissues, indicating a higher connectivity that reflects a higher efficiency of the anthocyanin pathway. Compared to light conditions, light exclusion reduced the total amount of anthocyanins, most severely in the skin of Gamay and to a lesser extent in the flesh and skin of Gamay Fréaux. Coordinated decrease in the transcript abundance of structural, regulatory and transporter genes by light exclusion correlated with the reduced anthocyanin concentration in a cultivar- and tissue-specific manner. Moreover, light exclusion increased the ratio of dihydroxylated to trihydroxylated anthocyanins, in parallel with F3'H and F3'5'H transcript amounts. Sugars and ABA only play a limited role in the control of anthocyanin synthesis in the berries, in contrast with what has been described in cell suspensions. This study provides novel insights into the regulation of anthocyanin in wild type and teinturier cultivars.

Effect of calcium on strawberry fruit flavonoid pathway gene expression and anthocyanin accumulation

Two diploid woodland strawberry (Fragaria vesca) inbred lines, Ruegen F7-4 (red fruit-bearing) and YW5AF7 (yellow fruit-bearing) were used to study the regulation of anthocyanin biosynthesis in fruit. Ruegen F7-4 fruit had similar total phenolics and anthocyanin contents to commercial octoploid (F. × ananassa) cultivar Seascape, while YW5AF7 exhibited relatively low total phenolics content and no anthocyanin accumulation. Foliar spray of CaCl2 boosted fruit total phenolics content, especially anthocyanins, by more than 20% in both Seascape and RF7-4. Expression levels of almost all the flavonoid pathway genes were comparable in Ruegen F7-4 and YW5AF7 green-stage fruit. However, at the turning and ripe stages, key anthocyanin structural genes, including flavanone 3-hydroxylase (F3H1), dihydroflavonol 4-reductase (DFR2), anthocyanidin synthase (ANS1), and UDP-glucosyltransferase (UGT1), were highly expressed in Ruegen F7-4 compared with YW5AF7 fruit. Calcium treatment further stimulated the expression of those genes in Ruegen F7-4 fruit. Anthocyanins isolated from petioles of YW5AF7 and Ruegen F-7 had the same HPLC-DAD profile, which differed from that of Ruegen F-7 fruit anthocyanins. All the anthocyanin structural genes except FvUGT1 were detected in petioles of YW5AF7 and Ruegen F-7. Taken together, these results indicate that the "yellow" gene in YW5AF7 is a fruit specific regulatory gene(s) for anthocyanin biosynthesis. Calcium can enhance accumulation of anthocyanins and total phenolics in fruit possibly via upregulation of anthocyanin structural genes. Our results also suggest that the anthocyanin biosynthesis machinery in petioles is different from that in fruit.

Characterization of ten date palm (Phoenix dactylifera L.) cultivars from Saudi Arabia using AFLP and ISSR markers

Date palm is the most economically important plant in the Middle East due to its nutritionally valuable fruit. The development of accurate DNA fingerprints to characterize cultivars and the detection of genetic diversity are of great value for breeding programs. The present study explores the usefulness of ISSR and AFLP molecular markers to detect relationships among 10 date palm (Phoenix dactylifera L.) cultivars from Saudi Arabia. Thirteen ISSR primers and six AFLP primer combinations were examined. The level of polymorphism among cultivars for ISSRs ranged from 20% to 100% with an average of 85%. Polymorphism levels for AFLPs ranged from 63% to 84% with an average of 76%. The total number of cultivar-specific markers was 241, 208 of which were generated from AFLP analysis. AJWA cultivar had the highest number of cultivar-specific ISSR markers, whereas DEK, PER, SUK-Q, SHA and MOS-H cultivars had the lowest. RAB and SHA cultivars had the most and least AFLP cultivar-specific markers, respectively. The highest pairwise similarity indices for ISSRs, AFLPs and combined markers were 84% between DEK (female) and PER (female), 81% between SUK-Q (male) and RAB (male), and 80% between SUK-Q (male) and RAB (male), respectively. The lowest similarity indices were 65% between TAB (female) and SUK-Q (male), 67% between SUK-A (female) and SUK-Q (male), and 67% between SUK-A (female) and SUK-Q (male). Cultivars of the same sex had higher pairwise similarities than those between cultivars of different sex. The Neighbor-Joining (NJ) tree generated from the ISSR dataset was not well resolved and bootstrap support for resolved nodes in the tree was low. AFLP and combined data generated completely resolved trees with high levels of bootstrap support. In conclusion, AFLP and ISSR approaches enabled discrimination among 10 date palm cultivars of from Saudi Arabia, which will provide valuable information for future improvement of this important crop.

Differential expression of flavonoid 3'-hydroxylase during fruit development establishes the different B-ring hydroxylation patterns of flavonoids in Fragaria × ananassa and Fragaria vesca

Flavonoid 3'-hydroxylase (F3'H) was studied for the first time in different Fragaria species. The cDNA clones isolated from unripe and ripe fruits of Fragaria x ananassa (garden strawberry) and Fragaria vesca (wild strawberry) showed high similarity (99% at the amino acid level) to the publically available F. vesca genome sequence and no significant differences could be identified between species and developmental stages of the fruits. In contrast, the genomic F3'H clones showed differences in the non-coding regions and 5'-flanking elements. The recombinant F3'Hs were functionally active and showed high specificity for naringenin, dihydrokaempferol, and kaempferol, whereas apigenin was only a minor substrate. During fruit development, a clear difference in the F3'H expression was observed between F. × ananassa and F. vesca. While a drastic decline of F3'H expression occurred during fruit ripening in F. × ananassa, F3'H in F. vesca was highly expressed in all stages. This was reflected by the anthocyanin composition, which showed a prevalence of pelargonidin in ripe fruits of F. × ananassa, whereas F. vesca had a high content of cyanidin. Screening of 17 berry species for their anthocyanin and flavonol composition showed that the prevalence of monohydroxylated anthocyanins makes garden strawberry unique among all other fruit species indicating that selection of bright red color during strawberry breeding, which consumers typically associate with freshness and ripeness, has selected phenotypes with a special biochemical background.

Why some fruits are green when they are ripe: carbon balance in fleshy fruits

Fruits that are green upon ripening ("green-ripe") tend to be dispersed by a limited range of frugivores, whereas those that are brightly colored ("bright-ripe") are dispersed by a wide range of birds and mammals. Because green fruits are probably less conspicuous than other colors of fruits, their pigmentation cannot be attributed to the attraction of seed dispersers. Instead, we hypothesize that a major benefit of green pigmentation is the ability to photosynthesize when ripe. Photosynthesis by fruits may lower their costs of production, and could result in fruits with greater nutrient reward. We present data on physical, chemical, and photosynthetic characteristics of ripe fleshy fruit of variable colors for 28 plant species at the La Selva Biological Station, Costa Rica. In addition to color and morphological characteristics of pulp and seeds, we report soluble solids content (refractive index), and photosynthetic/respiratory carbon-dioxide balance of ripe fruits. Carbon balance was much more dependent upon ambient light levels in green-ripe fruits than in bright-ripe fruit. In particular, data from light response curves indicated that green-ripe fruits may go into positive carbon balance at high light levels (above 300 μmol/m²/s). Rather than finding a positive relationship between soluble solids content and green fruit, as we predicted based on photosynthetic capacity, our data indicate that greater respiration rates of green-ripe fruits may result in carbon losses at low light levels. Our results were consistent with previously described morphological differences between the two color classes, with green-ripe fruits displaying significantly greater wet pulp mass, wet seed mass, and total fruit mass. Our data suggest that photosynthesis due to the retention of chlorophyll in ripe fleshy fruit may offset respiratory costs for plants with large or otherwise costly fruit, but this advantage should be evident only under high-light conditions.