Unveiling the regulatory role of DzAGL6-1 in carotenoid biosynthesis during durian (Durio zibethinus) fruit development.

KEY MESSAGE: Approximately 119 MADS-box genes have been identified in durian. Moreover, DzAGL6-1 primarily expressed during fruit development, activates the DzPSY promoter. Transient expression of DzAGL6-1 in tomatoes influences carotenoid production. MADS-box transcription factors play a crucial role in regulating plant biological processes, including fruit ripening and associated events. This study aimed to comprehend the mechanisms involved in durian fruit development and ripening and carotenoid production by conducting a genome-wide analysis of MADS-box proteins in durian (Durio zibethinus L.), an economically important fruit in Southeast Asia. A total of 119 durian MADS-box proteins were identified from the genome of the 'Musang King' cultivar. Based on the phylogenetic analysis, the proteins were classified into types I and II, which exhibited similar conserved motif compositions. Notably, only 16 durian MADS-box genes exhibited fruit-specific expression patterns. Among these genes, DzAGL6-1 was predominantly expressed during fruit development, a stage at which carotenoid biosynthesis is activated. Transient expression of DzAGL6-1 in tomato fruit increased the transcript level of the carotenoid biosynthetic gene phytoene synthase (PSY) and the ß-carotene content. Furthermore, DzAGL6-1 activated the promoter activity of DzPSY, as demonstrated by a dual-luciferase assay. These findings provide insights into the role of MADS-box transcription factors in regulating carotenoid biosynthesis during durian fruit development.

Comprehensive genome-wide analysis of calmodulin-binding transcription activator (CAMTA) in Durio zibethinus and identification of fruit ripening-associated DzCAMTAs.

BACKGROUND: Fruit ripening is an intricate developmental process driven by a highly coordinated action of complex hormonal networks. Ethylene is considered as the main phytohormone that regulates the ripening of climacteric fruits. Concomitantly, several ethylene-responsive transcription factors (TFs) are pivotal components of the regulatory network underlying fruit ripening. Calmodulin-binding transcription activator (CAMTA) is one such ethylene-induced TF implicated in various stress and plant developmental processes. RESULTS: Our comprehensive analysis of the CAMTA gene family in Durio zibethinus (durian, Dz) identified 10 CAMTAs with conserved domains. Phylogenetic analysis of DzCAMTAs, positioned DzCAMTA3 with its tomato ortholog that has already been validated for its role in the fruit ripening process through ethylene-mediated signaling. Furthermore, the transcriptome-wide analysis revealed DzCAMTA3 and DzCAMTA8 as the highest expressing durian CAMTA genes. These two DzCAMTAs possessed a distinct ripening-associated expression pattern during post-harvest ripening in Monthong, a durian cultivar native to Thailand. The expression profiling of DzCAMTA3 and DzCAMTA8 under natural ripening conditions and ethylene-induced/delayed ripening conditions substantiated their roles as ethylene-induced transcriptional activators of ripening. Similarly, auxin-suppressed expression of DzCAMTA3 and DzCAMTA8 confirmed their responsiveness to exogenous auxin treatment in a time-dependent manner. Accordingly, we propose that DzCAMTA3 and DzCAMTA8 synergistically crosstalk with ethylene during durian fruit ripening. In contrast, DzCAMTA3 and DzCAMTA8 antagonistically with auxin could affect the post-harvest ripening process in durian. Furthermore, DzCAMTA3 and DzCAMTA8 interacting genes contain significant CAMTA recognition motifs and regulated several pivotal fruit-ripening-associated pathways. CONCLUSION: Taken together, the present study contributes to an in-depth understanding of the structure and probable function of CAMTA genes in the post-harvest ripening of durian.

Combined effects of fermentation temperature and pH on kinetic changes of chemical constituents of durian wine fermented with Saccharomyces cerevisiae.

This study investigated the effects of temperature (20 and 30 °C) and pH (pH 3.1, 3.9) on kinetic changes of chemical constituents of the durian wine fermented with Saccharomyces cerevisiae. Temperature significantly affected growth of S. cerevisiae EC-1118 regardless of pH with a higher temperature leading to a faster cell death. The pH had a more significant effect on ethanol production than temperature with higher production at 20 °C (5.95%, v/v) and 30 °C (5.56%, v/v) at pH 3.9, relative to that at pH 3.1 (5.25 and 5.01%, v/v). However, relatively higher levels of isobutyl alcohol and isoamyl alcohol up to 64.52 ± 6.39 and 56.27 ± 3.00 mg/L, respectively, were produced at pH 3.1 than at pH 3.9 regardless of temperature. In contrast, production of esters was more affected by temperature than pH, where levels of ethyl esters (ethyl esters of octanoate, nonanoate, and decanoate) and acetate esters (ethyl acetate and isoamyl acetate) were significantly higher up to 2.13 ± 0.23 and 4.61 ± 0.22 mg/L, respectively, at 20 °C than at 30 °C. On the other hand, higher temperature improved the reduction of volatile sulfur compounds. This study illustrated that temperature control would be a more effective tool than pH in modulating the resulting aroma compound profile of durian wine.

Biotransformation of chemical constituents of durian wine with simultaneous alcoholic fermentation by Torulaspora delbrueckii and malolactic fermentation by Oenococcus oeni.

This work represents the first study on the biotransformation of chemical constituents of durian wine via simultaneous alcoholic fermentation (AF) and malolactic fermentation (MLF) with non-Saccharomyces yeast and lactic acid bacteria (LAB), namely, Torulaspora delbrueckii Biodiva and Oenococcus oeni PN4. The presence of PN4 improved the utilization of sugars but did not affect ethanol production. MLF resulted in the significant degradation of malic acid with corresponding increases in pH and lactic acid. The final concentrations of acetic acid (1.29 g/L) and succinic acid (3.70 g/L) in simultaneous AF and MLF were significantly higher than that in AF (1.05 and 1.31 g/L) only. Compared with AF, simultaneous AF and MLF significantly elevated the levels of aroma compounds with higher levels of higher alcohols (isoamyl alcohol, active amyl alcohol, isobutyl alcohol, and 2-phenylethyl alcohol), acetate esters (ethyl acetate, isoamyl acetate), and ethyl esters (ethyl octanoate, ethyl dodecanoate). All the endogenous volatile sulfur compounds decreased to trace or undetectable levels at the end of fermentation. MLF accentuated the reduction of acetaldehyde and sulfides. The initially absent dipropyl disulfide was formed, then catabolized, especially in simultaneous AF and MLF. This study suggested that the simultaneous AF and MLF of non-Saccharomyces and LAB could modify the volatile compositions and potentially modulate the organoleptic properties of durian wine.

Physio-chemical, microbiological properties of tempoyak and molecular characterisation of lactic acid bacteria isolated from tempoyak.

This study aims to determine physio-chemical properties of tempoyak, characterise the various indigenous species of lactic acid bacteria (LAB) present at different stages of fermentation and also to determine the survival of selected foodborne pathogens in tempoyak. The predominant microorganisms present in tempoyak were LAB (8.88-10.42 log CFU/g). Fructobacillus durionis and Lactobacillus plantarum were the dominant members of LAB. Other LAB species detected for the first time in tempoyak were a fructophilic strain of Lactobacillus fructivorans, Leuconostoc dextranicum, Lactobacillus collinoides and Lactobacillus paracasei. Heterofermentative Leuconostoc mesenteroides and F. durionis were predominant in the initial stage of fermentation, and as fermentation proceeded, F. durionis remained predominant, but towards the end of fermentation, homofermentative Lb. plantarum became the predominant species. Lactic, acetic and propionic acids were present in concentrations ranging from 0.30 to 9.65, 0.51 to 7.14 and 3.90 to 7.31 mg/g, respectively. Genotyping showed a high degree of diversity among F. durionis and Lb. plantarum isolates, suggesting different sources of LAB. All tested Lb. plantarum and F. durionis (except for one isolate) isolates were multidrug resistant. Salmonella spp., Listeria monocytogenes and Staphylococcus aureus were not detected. However, survival study showed that these pathogens could survive up to 8-12 days. The results aiming at improving the quality and safety of tempoyak.

Characterization of alcohol acetyltransferases in the ripe flesh of 'Monthong' and 'Chanthaburi 1' durians.

Durian is economically significant in Southeast Asia due to its distinctive aroma and palatability. During fruit ripening, the flesh generates a substantial quantity of esters and some sulfur-containing compounds. This study aimed to analyze the ester profiles and characteristics of alcohol acetyltransferase (AAT; EC. 2.3.1.84) in the ripe flesh of two Thai durian (Durio zibethinus Merr.) cultivars, 'Chanthaburi 1' (a hybrid cultivar with a soft aroma) and 'Monthong' (a renowned cultivar with a medium scent). The primary esters responsible for the aromatic compounds found in durian are ethyl-2-methyl butanoate, ethyl hexanoate, and ethyl octanoate. The AAT's efficacy was assessed in its ability to catalyze the synthesis of acetate esters through the reaction between acetyl CoA and different alcohols. The AAT enzymes extracted from 'Chanthaburi 1' and 'Monthong' cultivars exhibited a notable affinity towards 3-methyl-1-butanol and hexanol as alcohol substrates. Propanol and butanol exhibited moderate activity as AAT substrates, whereas methanol and ethanol demonstrated the lowest. Both durians exhibited favorable enzyme activity at a temperature of 30 °C. However, 'Monthong' AAT demonstrated superior performance across a broader pH range compared to 'Chanthaburi 1' AAT. The partially purified proteins precipitated with ammonium sulfate and subsequently gel-filtered through a DEAE-Sephadex® column enhanced the potency of 'Chanthaburi 1' AAT, resulting in increased purity (1.20-fold) and specificity (1.08-fold) compared to 'Monthong'. The AAT of 'Chanthaburi 1' and 'Monthong' exhibited molecular weights of 39.52 and 41.51 kDa, respectively. This study presents the initial documentation of AAT in durians through an enzyme assay and activity staining technique.

Elucidation of the Anticancer Mechanism of Durian Fruit (Durio zibethinus) Pulp Extract in Human Leukemia (HL-60) Cancer Cells.

Durian (Durio zibethinus L.) grows widely in Southeast Asia. The pulp of the durian fruit contains carbohydrates, proteins, lipids, fibers, various vitamins, minerals, and fatty acids. This study was carried out to elucidate the anticancer mechanism of action of the methanolic extract of the fruit of Durio zibethinus (D. zibethinus) on human leukemia (HL-60) cells. The methanolic extract of D. zibethinus fruits exhibited its anticancer effect on HL-60 cells by inducing DNA damage and apoptosis. The DNA damage was confirmed by comet and DNA fragmentation assays. The methanolic extract of D. zibethinus fruits has been shown to cause cell cycle arrest in HL-60 cells during the S phase and G2/M phase. Additionally, the methanolic extract caused induction of the apoptotic pathway in the HL-60 cell line. This was confirmed by increased expression in pro-apoptotic proteins, viz., Bax protein expression, and a substantial reduction (p < 0.001) in anti-apoptotic proteins, viz., Bcl-2 and Bcl-xL expressions. Therefore, this study confirms that the methanolic extract of D. zibethinus exerts its anticancer effects on the HL-60 cell line, causing cell cycle arrest and induction of apoptosis by an intrinsic mechanism.

Transcriptome-wide identification and expression profiling of the ERF gene family suggest roles as transcriptional activators and repressors of fruit ripening in durian.

The involvement of the phytohormone ethylene as the main trigger of climacteric fruit ripening is well documented. However, our knowledge regarding the role of ethylene response factor (ERF) transcription factor in the transcriptional regulation of ethylene biosynthesis during fruit ripening remains limited. Here, comprehensive transcriptome analysis and expression profiling revealed 63 ERFs in durian pulps, termed DzERF1-DzERF63, of which 34 exhibited ripening-associated expression patterns at three stages (unripe, midripe, and ripe) during fruit ripening. Hierarchical clustering analysis classified 34 ripening-associated DzERFs into three distinct clades, among which, clade I consisted of downregulated DzERFs and clade III included those upregulated during ripening. Phylogenetic analysis predicted the functions of some DzERFs based on orthologs of previously characterized ERFs. Among downregulated DzERFs, DzERF6 functional prediction revealed its role as a negative regulator of ripening via ethylene biosynthetic gene repression, whereas among upregulated genes, DzERF9 was predicted to positively regulate ethylene biosynthesis. Correlation network analysis of 34 ripening-associated DzERFs with potential target genes revealed a strong negative correlation between DzERF6 and ethylene biosynthetic genes and a strong positive correlation between DzERF9 and ethylene biosynthesis. DzERF6 and DzERF9 showed differential expression patterns in association with different ripening treatments (natural, ethylene-induced, and 1-methylcyclopropene-delayed ripening). DzERF6 was downregulated, whereas DzERF9 was upregulated, during ripening and after ethylene treatment. The auxin-repressed and auxin-induced expression of DzERF6 and DzERF9, respectively, confirmed its dose-dependent responsiveness to exogenous auxin. We suggest ethylene- and auxin-mediated roles of DzERF6 and DzERF9 during fruit ripening, possibly through transcriptional regulation of ethylene biosynthetic genes.

Identification of an Important Odorant Precursor in Durian: First Evidence of Ethionine in Plants.

On the basis of the following data from the literature, we hypothesized the presence of ethionine in durian pulp: (1) the major odorants in terms of quantity as well as odor potency in durian pulp are ethanethiol and its derivatives; (2) genome analysis of durian assigned methionine γ-lyase (MGL), the enzyme that converts methionine to methanethiol, a key role for durian odor formation; and (3) MGL accepts not only methionine but also ethionine as a substrate. A targeted search by liquid chromatography-tandem mass spectrometry allowed us to confirm the presence of ethionine in durian pulp. Quantitation of ethionine in samples of different varieties (Monthong, Krathum, Chanee, and Kanyao) showed concentrations (621-9600 µg/kg) in the same range but below the methionine concentrations (16100-30200 µg/kg). During fruit ripening, the ethionine concentration increased as well as the ethanethiol concentration. Final evidence for the role of ethionine as an ethanethiol precursor was provided by demonstrating the formation of (2H5)ethanethiol after adding (2H5)ethionine to durian pulp.

Glycolytic genes expression, proapoptotic potential in relation to the total content of bioactive compounds in durian fruits.

The properties of durian fruit at five stages of ripeness were evaluated and compared. The physicochemical parameters such as titratable acidity (TA) and total soluble solids (TSS) increased, whereas the pH slightly decreased during the ripening process. The highest contents of polyphenols, flavonoids, flavanols, tannins, vitamin C and the antioxidant capacities, measured by radical scavenging assays, were found in ripe and overripe fruits. The structural properties of extracted polyphenols were evaluated by Fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. The interaction of polyphenols with the main drug carrier in blood human serum albumin (HSA) showed decrease in its fluorescence intensity. The binding properties of polyphenols were in direct correlation with the antioxidant capacities of the investigated fruits. HepG2 cells evaluated cytotoxic effect and the mechanism of cell death after treatment with durian. The metabolism of carbohydrates was examined on the expression of glycolysis-related genes (hexokinase 2 (HK2); 6-phosphofructo-2-kinase 4 (PFKFB4); facilitated glucose transporter member 1 (SLC2A1 (Glut1)) and lactate dehydrogenase A and utilization of glucose in the hepatocytes with durian treatment. Durian in immature stage had stronger cytotoxic effect and weak proapoptotic potential on HepG2 cells than the mature and overripe ones. The ripe and overripe fruits increased the expression of hepatic HK2 and PFKFB4 glycolytic genes and stimulated glucose utilization in HepG2 cells. The present results indicate that durians reveal different biological activity and may provide their broad and extensive use as medicinal or functional foods.

Metabolic variation in the pulps of two durian cultivars: Unraveling the metabolites that contribute to the flavor.

Durian (Durio zibethinus M.) is a major economic fruit crop in Thailand. In this study, two popular cultivars, namely Chanee and Mon Thong, were collected from three orchards located in eastern Thailand. The pulp metabolome, including 157 annotated metabolites, was explored using capillary electrophoresis-time of flight/mass spectrometry (CE-TOF/MS). Cultivars and harvest years had more impact on metabolite profile separation than cultivation areas. We identified cultivar-dependent metabolite markers related to durian fruit quality traits, such as nutritional value (pyridoxamine), odor (cysteine, leucine), and ripening process (aminocyclopropane carboxylic acid). Interestingly, durian fruit were found to contain high amounts of γ-glutamylcysteine (810.3 ±â€¯257.5 mg/100 g dry weight) and glutathione (158.1 ±â€¯80.4 mg/100 g dry weight), which act as antioxidants and taste enhancers. This metabolite information could be related to consumer preferences and exploited for durian fruit quality improvement.

The effect of 1-methylcyclopropene (1-MCP) on expression of ethylene receptor genes in durian pulp during ripening.

Rapid fruit ripening is a significant problem that limits the shelf life of durian, with ethylene having a major impact on the regulation of this event. Durian treated with ethephon ripened 3 d after treatment with increased pulp total soluble solids, ethylene production of the whole fruit and decreased pulp firmness compared to the control fruit. 1-MCP treatment delayed ripening by up to 9 d with inhibited accumulation of total soluble solids, color change, softening and ethylene production. Genes related to ethylene perception (DzETR1 and DzETR2) and the signaling pathway (DzCTR1, DzEIL1 and DzEIL2) in the pulp were investigated during this process, using qPCR to quantify changes in gene transcription. All candidate genes were significantly up-regulated in ripening durian pulp. Ethephon treatment increased the expression of DzETR1 and DzETR2 genes, while expression of DzCTR1, DzEIL1 and DzEIL2 were slightly affected. 1-MCP treatment significantly inhibited the expression of the DzETR2 and DzEIL1 genes. The promoters of DzETR2 genes were isolated and their activation by fruit transcription factors studied using transient expression in tobacco leaves. It was found that members of the kiwifruit and apple EIL1, EIL2 and EIL3 genes strongly activated the DzETR2 promoter. These results suggest that ethylene-induced ripening of durian is via the regulation of DzETR2 by EIL transcription factors.

A novel non-dairy beverage from durian pulp fermented with selected probiotics and yeast.

This study investigated the effects of sequential inoculation (Seq-I) of Bifidobacterium animalis subsp. lactis or Lactobacillus casei with yeast Williopsis saturnus on durian pulp fermentation. Seq-I of W. saturnus following B. animalis subsp. lactis did not bring about any significant differences compared to the B. animalis subsp. lactis monoculture due to the sharp early death of W. saturnus soon after inoculation. However, Seq-I of W. saturnus significantly enhanced the survival of L. casei and improved the utilization of fructose and glucose compared to L. casei monoculture. In addition, there were significant differences in the metabolism of organic acids especially for lactic acid and succinic acid. Furthermore, Seq-I produced significantly higher levels of volatile compounds including alcohols (ethanol and 2-phenylethyl alcohol) and acetate esters (2-phenylethyl acetate, isoamyl acetate and ethyl acetate), which would positively contribute to the flavour notes. Although the initial volatile sulphur compounds were reduced to trace levels after fermentation, but the durian odour still remained. This study suggests that the use of probiotics and W. saturnus to ferment durian pulp could act as a potential avenue to develop a novel non-dairy durian-based functional beverage to deliver probiotics.

Chemical consequences of three commercial strains of Oenococcus oeni co-inoculated with Torulaspora delbrueckii in durian wine fermentation.

This work evaluated for the first time the chemical consequences of three commercial strains of Oenococcus oeni co-inoculated with Torulaspora delbrueckii in durian wine fermentation. Compared with the control (yeast only, 5.70% v/v ethanol produced), samples co-inoculated with T. delbrueckii and O. oeni PN4 improved ethanol production (6.06% v/v), which was significantly higher than samples co-inoculated with Viniflora (4.78% v/v) or Enoferm Beta (5.01% v/v). Wines co-fermented with the respective latter two oenococci contained excessive levels of ethyl acetate (>80mg/L) that were likely to affect negatively wine aroma. In addition, they led to significantly higher acetic and lactic acid production relative to PN4. O. oeni PN4 seemed to be the most suitable strain to co-inoculate with T. delbrueckii for simultaneous alcoholic and malolactic fermentation in durian wine by contributing moderately increased concentrations of higher alcohols, acetate esters and ethyl esters that would have positive sensory impacts.

Carotenoid accumulation in durian (Durio zibethinus) fruit is affected by ethylene via modulation of carotenoid pathway gene expression.

Carotenoid content in durian (Durio zibethinus) fruit is an important aspect of fruit quality, with different cultivars distinguished by differing pigmentation. We have studied the dependence of carotenogenesis on ethylene. Fruit of the cultivar 'Chanee' harvested at the mature stage were either left untreated (controls), treated with 1-methylcyclopropene (1-MCP) for 12 h, or treated with application of an aqueous ethephon solution to the stem end, or treated for 12 h with 1-MCP followed by ethephon application. Fruit were then stored for 9 d at 25 °C. Pulp color of durian became steadily yellowish as a result of accumulation of carotenoids, which were mainly beta-carotene, and alpha-carotene, with a minor amount of zeaxanthin and lutein. 1-MCP delayed the increase in the accumulation of beta-carotene, alpha-carotene, and zeaxanthin, but not lutein. In contrast, ethephon had no significant effect on carotenoid accumulation. The expression of zeta-carotene desaturase (ZDS), lycopene beta-cyclase (LCYB), chromoplast specific lycopene beta-cyclase (CYCB) and beta-carotene hydroxylase (BCH) genes was highly correlated with carotenoid content and pulp color.1-MCP resulted in significant down-regulation of ZDS, LCYB, CYCB and BCH expression. The accumulation of beta-carotene and alpha-carotene appears to be controlled by the level of expression of LCYB gene, whose function was tested in bacteria to show conversion of lycopene and delta-carotene to beta-carotene and alpha-carotene, respectively. These results suggest that ripening-induced carotenoid accumulation is regulated by endogenous ethylene controlling the expression of key genes such as LCYB.

The draft genome of tropical fruit durian (Durio zibethinus).

Durian (Durio zibethinus) is a Southeast Asian tropical plant known for its hefty, spine-covered fruit and sulfury and onion-like odor. Here we present a draft genome assembly of D. zibethinus, representing the third plant genus in the Malvales order and first in the Helicteroideae subfamily to be sequenced. Single-molecule sequencing and chromosome contact maps enabled assembly of the highly heterozygous durian genome at chromosome-scale resolution. Transcriptomic analysis showed upregulation of sulfur-, ethylene-, and lipid-related pathways in durian fruits. We observed paleopolyploidization events shared by durian and cotton and durian-specific gene expansions in MGL (methionine γ-lyase), associated with production of volatile sulfur compounds (VSCs). MGL and the ethylene-related gene ACS (aminocyclopropane-1-carboxylic acid synthase) were upregulated in fruits concomitantly with their downstream metabolites (VSCs and ethylene), suggesting a potential association between ethylene biosynthesis and methionine regeneration via the Yang cycle. The durian genome provides a resource for tropical fruit biology and agronomy.

Induction of simultaneous and sequential malolactic fermentation in durian wine.

This study represented for the first time the impact of malolactic fermentation (MLF) induced by Oenococcus oeni and its inoculation strategies (simultaneous vs. sequential) on the fermentation performance as well as aroma compound profile of durian wine. There was no negative impact of simultaneous inoculation of O. oeni and Saccharomyces cerevisiae on the growth and fermentation kinetics of S. cerevisiae as compared to sequential fermentation. Simultaneous MLF did not lead to an excessive increase in volatile acidity as compared to sequential MLF. The kinetic changes of organic acids (i.e. malic, lactic, succinic, acetic and α-ketoglutaric acids) varied with simultaneous and sequential MLF relative to yeast alone. MLF, regardless of inoculation mode, resulted in higher production of fermentation-derived volatiles as compared to control (alcoholic fermentation only), including esters, volatile fatty acids, and terpenes, except for higher alcohols. Most indigenous volatile sulphur compounds in durian were decreased to trace levels with little differences among the control, simultaneous and sequential MLF. Among the different wines, the wine with simultaneous MLF had higher concentrations of terpenes and acetate esters while sequential MLF had increased concentrations of medium- and long-chain ethyl esters. Relative to alcoholic fermentation only, both simultaneous and sequential MLF reduced acetaldehyde substantially with sequential MLF being more effective. These findings illustrate that MLF is an effective and novel way of modulating the volatile and aroma compound profile of durian wine.

Comparison of aroma-active compounds and sensory characteristics of durian (Durio zibethinus L.) wines using strains of Saccharomyces cerevisiae with odor activity values and partial least-squares regression.

The study evaluated the effects of five different strains (GRE, RC212, Lalvin D254, CGMCC2.4, and CGMCC2.23) of the yeast Saccharomyces cerevisiae on the aromatic characteristics of fermented durian musts. In this work, 38 and 43 compounds in durian juices and wines were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-pulsed flame photometric detection (GC-PFPD) with the aid of stir bar sorptive extraction (SBSE), respectively. According to the measured odor activity values (OAV), only 11 and 15 aroma compounds had OAVs >1 in durian juices or wines, among which 2,3-butanedione, 3-methylbutanol, dimethyl sulfide, dimethyl disulfide, methyl ethyl disulfide, ethyl 2-methylbutanoate, ethyl butanoate, and ethyl octanoate were major contributors to the aroma of juices and wines. Partial least-squares regression (PLSR) was used to detect positive correlations between sensory analysis and aroma compounds. The results showed that the attributes were closely related to aroma compounds.

Expression of expansin genes in the pulp and the dehiscence zone of ripening durian (Durio zibethinus) fruit.

Durian (Durio zibethinus) fruit was harvested at the commercially mature stage and stored at 25°C. Durian fruit have 3-5 longitudinal dehiscence zones (DZs) in the peel, which are up to 40cm long and 2cm thick in large fruit. Dehiscence started a week after harvest, was hastened by exogenous ethylene, and delayed by 1-methylcyclopropene (1-MCP), showing that it is regulated by endogenous ethylene. Three genes encoding α-expansins (DzEXP1-3) were isolated. In the expression of these genes increased, prior to dehiscence. Pulp firmness decreased during storage. The decrease was hastened by ethylene and delayed by 1-methylcyclopropene (1-MCP). Exogenous ethylene promoted gene expression of DzEXP1 both in the DZs and in the pulp. It had a smaller effect on DzEXP2 in the zones and pulp, but did not affect DzEXP3 expression. 1-MCP inhibited the expression of DzEXP1 and, somewhat less, of DzEXP2, but did not affect DzEXP3 expression, both in DZs and pulp. It is concluded that the close relationship between expression of DzEXP1 and DzEXP2 and both dehiscence and fruit softening suggests that these genes are involved in both processes.

Accumulation of Isohemigossypolone and Its Related Compounds in the Inner Bark and Heartwood of Diseased Pachira aquatica.

Isohemigossypolone (1) and 2-O-methylisohemigossypolone (2), major fungitoxins of Pachira aquatica, were found to accumulate locally in the outer bark of the swollen trunk, whereas the inner bark and heartwood contained only a trace amount of them. From P. aquatica that was infected with a phytopathogenic bacterium, we detected significant amounts of 1 and 2 from browned inner tissues of the swollen trunk. According to a quantitative analysis by a gas-chromatograph, the concentration of 1 in the diseased inner tissues was calculated to be approximately 780 µg/g f.w., which was the same level as that in the outer bark of healthy individuals. These findings suggest that the inner tissues inducibly produced and accumulated antifungals 1 and 2 during infection events, as do many plants with phytoalexins. 11-Nor-2-O-methylisohemigossypolone (3), showing approximately equivalent fungitoxic activity to that of 1 and 2, was also isolated from the infected inner tissues. We screened pathogenic bacteria from the infected tissue, and isolated a rod-shaped bacterium that was tentatively identified as Pseudomonas sp. which promoted tissue-browning on sectioned disks of P. aquatica trunks.