Isolation of ripening-related genes from ethylene/1-MCP treated papaya through RNA-seq

MaBEL1 regulates banana fruit ripening by activating cell wall and starch degradation-related genes

Banana is a typical subtropical fruit, sensitive to chilling injuries and prone to softening disorder. However, the underlying regulatory mechanisms of the softening disorder caused by cold stress remain obscure. Herein, we found that BEL1-LIKE HOMEODOMAIN transcription factor 1 (MaBEL1) and its associated proteins regulate the fruit softening and ripening process. The transcript and protein levels of MaBEL1 were up-regulated with fruit ripening but severely repressed by the chilling stress. Moreover, the MaBEL1 protein interacted directly with the promoters of the cell wall and starch degradation-related genes, such as MaAMY3, MaXYL32, and MaEXP-A8. The transient overexpression of MaBEL1 alleviated fruit chilling injury and ripening disorder caused by cold stress and promoted fruit softening and ripening of "Fenjiao" banana by inducing ethylene production and starch and cell wall degradation. The accelerated ripening was also validated by the ectopic overexpression in tomatoes. Conversely, MaBEL1-silencing aggravated the chilling injury and ripening disorder and repressed fruit softening and ripening by inhibiting ethylene production and starch and cell wall degradation. MaABI5-like and MaEBF1, the two positive regulators of the fruit softening process, interacted with MaBEL1 to enhance the promoter activity of the starch and cell wall degradation-related genes. Moreover, the F-box protein MaEBF1 does not modulate the degradation of MaBEL1, which regulates the transcription of MaABI5-like protein. Overall, we report a novel MaBEL1-MaEBF1-MaABI5-like complex system that mediates the fruit softening and ripening disorder in "Fenjiao" bananas caused by cold stress.

Pectate Lyase Gene VvPL1 Plays a Role in Fruit Cracking of Table Grapes

Fruit cracking seriously affects the commercial value of table grapes. To explore whether cell wall disassembly influences grape berry cracking, first, the differences in the cell wall metabolism were compared between cracking-resistant "Shennongjinhuanghou" (SN) and cracking-susceptible "Xiangfei" (XF) varieties. Our results showed that cell wall disassembly events were extremely different between "SN" and "XF." The cracking-resistant "SN" had a higher pectinmethylesterase activity in the early stage and lower polygalacturonase, β-galactosidase, pectate lyase, and cellulase activities from veraison, cooperatively yielding higher ionically bound pectin, covalently bound pectin, hemicellulose, and lower water-soluble pectin, leading to a stronger skin break force and elasticity and conferring "SN" with higher cracking resistance. Furthermore, the function of the VvPL1 gene in fruit cracking was verified by heterologously transforming tomatoes. The transgenic experiment showed that overexpressed fruits had a higher activity of pectate lyase from the breaking stage and a lower level of covalently bound pectin, ionically bound pectin, cellulose, and hemicellulose and a higher level of water-soluble pectin at the red ripe stage, which resulted in a significantly reduced skin break force and flesh firmness and increased fruit cracking incidences. In conclusion, our results demonstrated that the cracking susceptibility of the grape berry is closely related to cell wall disassembly events and VvPL1 plays an important role in fruit cracking.

Transcription Factor CpbHLH3 and CpXYN1 Gene Cooperatively Regulate Fruit Texture and Counteract 1-Methylcyclopropene Inhibition of Softening in Postharvest Papaya (Carica papaya L.)

Papaya (Carica papaya L.) is a climacteric fruit susceptible to postharvest losses attributable to ethylene-induced ripening and softening. In this study, we examined the effect of 1-methylcyclopropene (1-MCP) treatment (1 μL L^-1 for 20 h) on the textural properties of "SunUp" papaya fruit and investigated the regulatory mechanisms of molecular profiles. Compared with control, postharvest 1-MCP treatment significantly inhibited fruit softening, which is associated with higher hemicellulose content and lower xylanase activity of papaya fruit. Moreover, RNA-seq and qRT-PCR analyses indicated that CpbHLH3 and CpXYN1 were differentially expressed during storage. Yeast one-hybrid, electrophoretic mobility shift assays, and dual-luciferase reporter assays disclosed that CpbHLH3 activated the transcription of CpXYN1 by binding directly to its promoter. Transient overexpression of CpbHLH3 alleviates the inhibitory effect of 1-MCP on softening by increasing xylanase activity and upregulating the gene expression. Our observations provide new insights into the transcriptional regulatory mechanisms that govern softening of postharvest papaya fruit.

Quantitative Ubiquitylomic Analysis of the Dynamic Changes and Extensive Modulation of Ubiquitylation in Papaya During the Fruit Ripening Process

Lysine ubiquitination is a highly conserved post-translational modification with diverse biological functions. However, there is little available information on lysine ubiquitination of non-histone proteins in papaya (Carica papaya L.). In total, 3,090 ubiquitination sites on 1,249 proteins with diverse localizations and functions were identified. Five conserved ubiquitinated K motifs were identified. Enrichment analysis showed that many Hsps were differentially ubiquitinated proteins (DUPs), suggesting an essential role of ubiquitination in degradation of molecular chaperone. Furthermore, 12 sugar metabolism-related enzymes were identified as DUPs, including an involvement of ubiquitination in nutrimental changes during the papaya ripening process. The ubiquitination levels of five fruit ripening-related DUPs, including one ethylene-inducible protein, two 1-aminocyclopropane-1-carboxylic acid oxidases, one endochitinase, and one cell wall invertase, were significantly changed during the ripening process. Our study extends the understanding of diverse functions for lysine ubiquitination in regulation of the papaya fruit ripening process.

Xyloglucan endotransglucosylase/hydrolase genes LcXTH4/7/19 are involved in fruitlet abscission and are activated by LcEIL2/3 in litchi

Organ abscission in plants requires the hydrolysis of cell wall components, mainly including celluloses, pectins, and xyloglucans. However, how the genes that encode those hydrolytic enzymes are regulated and their function in abscission remains unclear. Previously we revealed that two cellulase genes LcCEL2/8 and two polygalacturonase genes LcPG1/2 were responsible for the degradation of celluloses and pectins, respectively, during fruitlet abscission in litchi. Here, we further identified three xyloglucan endotransglucosylase/hydrolase genes (LcXTH4, LcXTH7, LcXTH19) that are also involved in this process. Nineteen LcXTHs, named LcXTH1-19, were identified in the litchi genome. Transcriptome data and qRT-PCR confirmed that LcXTH4/7/19 were significantly induced at the abscission zone (AZ) during fruitlet abscission in litchi. The GUS reporter driven by each promoter of LcXTH4/7/19 was specifically expressed at the floral abscission zone of Arabidopsis, and importantly ectopic expression of LcXTH19 in Arabidopsis resulted in precocious floral organ abscission. Moreover, electrophoretic mobility shift assay (EMSA) and dual-luciferase reporter analysis showed that the expression of LcXTH4/7/19 could be directly activated by two ETHYLENE INSENSITIVE 3-like (EIL) transcription factors LcEIL2/3. Collectively, we propose that LcXTH4/7/19 are involved in fruitlet abscission, and LcEIL2/3-mediated transcriptional regulation of diverse cell wall hydrolytic genes is responsible for this process in litchi.

Papaya (Carica papaya L.) Flavour Profiling

A major challenge to the papaya industry is inconsistency in fruit quality and, in particular, flavour, which is a complex trait that comprises taste perception in the mouth (sweetness, acidity, or bitterness) and aroma produced by several volatile compounds. Current commercial varieties vary greatly in their taste, likely due to historical prioritised selection for fruit appearance as well as large environmental effects. Therefore, it is important to better understand the genetic and biochemical mechanisms and biosynthesis pathways underpinning preferable flavour in order to select and breed for better tasting new commercial papaya varieties. As an initial step, objectively measurable standards of the compound profiles that provide papaya's taste and aroma, together with 'mouth feel', are required. This review presents an overview of the approaches to characterise the flavour profiles of papaya through sugar component determination, volatile compound detection, sensory panel testing, as well as genomics-based studies to identify the papaya flavour.

Systems Biology Applied to the Study of Papaya Fruit Ripening: The Influence of Ethylene on Pulp Softening

Papaya is a fleshy fruit that undergoes fast ethylene-induced modifications. The fruit becomes edible, but the fast pulp softening is the main factor that limits the post-harvest period. Papaya fast pulp softening occurs due to cell wall disassembling coordinated by ethylene triggering that massively expresses pectinases. In this work, RNA-seq analysis of ethylene-treated and non-treated papayas enabled a wide transcriptome overview that indicated the role of ethylene during ripening at the gene expression level. Several families of transcription factors (AP2/ERF, NAC, and MADS-box) were differentially expressed. ACO, ACS, and SAM-Mtase genes were upregulated, indicating a high rate of ethylene biosynthesis after ethylene treatment. The correlation among gene expression and physiological data demonstrated ethylene treatment can indeed simulate ripening, and regulation of changes in fruit color, aroma, and flavor could be attributed to the coordinated expression of several related genes. Especially about pulp firmness, the identification of 157 expressed genes related to cell wall metabolism demonstrated that pulp softening is accomplished by a coordinated action of several different cell wall-related enzymes. The mechanism is different from other commercially important fruits, such as strawberry, tomato, kiwifruit, and apple. The observed behavior of this new transcriptomic data confirms ethylene triggering is the main event that elicits fast pulp softening in papayas.

Transcriptomic analysis reveals key transcription factors associated to drought tolerance in a wild papaya (Carica papaya) genotype

Most of the commercial papaya genotypes show susceptibility to water deficit stress and require high volumes of irrigation water to yield properly. To tackle this problem, we have collected wild native genotypes of Carica papaya that have proved to show better physiological performance under water deficit stress than the commercial cultivar grown in Mexico. In the present study, plants from a wild Carica papaya genotype and a commercial genotype were subjected to water deficit stress (WDS), and their response was characterized in physiological and molecular terms. The physiological parameters measured (water potential, photosynthesis, Fv/Fm and electrolyte leakage) confirmed that the papaya wild genotype showed better physiological responses than the commercial one when exposed to WDS. Subsequently, RNA-Seq was performed for 4 cDNA libraries in both genotypes (susceptible and tolerant) under well-watered conditions, and when they were subjected to WDS for 14 days. Consistently, differential expression analysis revealed that after 14 days of WDS, the wild tolerant genotype had a higher number of up-regulated genes, and a higher number of transcription factors (TF) that were differentially expressed in response to WDS, than the commercial genotype. Thus, six TF genes (CpHSF, CpMYB, CpNAC, CpNFY-A, CpERF and CpWRKY) were selected for further qRT-PCR analysis as they were highly expressed in response to WDS in the wild papaya genotype. qRT-PCR results confirmed that the wild genotype had higher expression levels (REL) in all 6 TF genes than the commercial genotype. Our transcriptomic analysis should help to unravel candidate genes that may be useful in the development of new drought-tolerant cultivars of this important tropical crop.

Discovery of SNPs and InDels in papaya genotypes and its potential for marker assisted selection of fruit quality traits

Papaya is a tropical and climacteric fruit that is recognized for its nutritional benefits and medicinal applications. Its fruits ripen quickly and show a drastic fruit softening, leading to great post-harvest losses. To overcome this scenario, breeding programs of papaya must invest in exploring the available genetic variation to continue developing superior cultivars with improved fruit quality traits. The objective of this study was to perform a whole-genome genotyping (WGG) of papaya, predict the effects of the identified variants, and develop a list of ripening-related genes (RRGs) with linked variants. The Formosa elite lines of papaya Sekati and JS-12 were submitted to WGG with an Illumina Miseq platform. The effects of variants were predicted using the snpEff program. A total of 28,451 SNPs having Ts/Tv (Transition/Transversion) ratio of 2.45 and 1,982 small insertions/deletions (InDels) were identified. Most variant effects were predicted in non-coding regions, with only 2,104 and 138 effects placed in exons and splice site regions, respectively. A total of 106 RRGs were found to be associated with 460 variants, which may be converted into PCR markers to facilitate genetic mapping and diversity studies and to apply marker-assisted selection (MAS) for specific traits in papaya breeding programs.

Demethylation alters transcriptome profiling of buds and leaves in 'Kyoho' grape

BACKGROUND

Grape buds and leaves are directly associated with the physiology and metabolic activities of the plant, which is monitored by epigenetic modifications induced by environment and endogenous factors. Methylation is one of the epigenetic regulators that could be involved in DNA levels and affect gene expression in response to stimuli. Therefore, changes of gene expression profile in leaves and bud through inhibitors of DNA methylation provide a deep understanding of epigenetic effects in regulatory networks.

RESULTS

In this study, we carried out a transcriptome analysis of 'Kyoho' buds and leaves under 5-azacytidine (5-azaC) exposure and screened a large number of differentially expressed genes (DEGs). GO and KEGG annotations showed that they are mainly involved in photosynthesis, flavonoid synthesis, glutathione metabolism, and other metabolic processes. Functional enrichment analysis also provided a holistic perspective on the transcriptome profile when 5-azaC bound to methyltransferase and induced demethylation. Enrichment analysis of transcription factors (TFs) also showed that the MYB, C2H2, and bHLH families are involved in the regulation of responsive genes under epigenetic changes. Furthermore, hormone-related genes have also undergone significant changes, especially gibberellin (GA) and abscisic acid (ABA)-related genes that responded to bud germination. We also used protein-protein interaction network to determine hub proteins in response to demethylation.

CONCLUSIONS

These findings provide new insights into the establishment of molecular regulatory networks according to how methylation as an epigenetic modification alters transcriptome patterns in bud and leaves of grape.

Transcriptome analysis of metabolisms related to fruit cracking during ripening of a cracking-susceptible grape berry cv. Xiangfei (Vitis vinifera L.)

BACKGROUND

Grape is an economically valuable fruit around the world. However, some cultivars are prone to fruit cracking during ripening, leading to severe losses.

OBJECTIVE

We aimed to find important metabolisms related to fruit cracking during ripening process.

METHODS

RNA-Sequence and analysis was applied to the pericarp of cracking-susceptible 'Xiang Fei' at 1 (W1), 2 (W2) and 3 weeks (W3) after veraison on Illumina HiSeq xten; RESULTS: Compared with W1, the berry cracking rate increased significantly in W2 and W3. Through transcriptomic analysis, a total of 22,609 genes were expressed in the grape pericarp, among which 805 and 2758 genes were significantly differentially regulated in W1-vs.-W2 and W1-vs.-W3 comparison, respectively. Besides, 304 and 354 genes were up- and down-regulated in both comparisons. The significantly enriched GO terms of both W1-W2 and W1-W3 are related to cell wall and wax biosynthesis. And lipid metabolism, which are involved in the top 20 enriched KEGG pathways of both comparisons, was related to wax biosynthesis. Further, GO enrichment analysis of differentially expressed genes (DEGs) with same regulatory changes also indicated that the continuously up-regulated DEGs are significantly enriched in cell wall component biosynthesis and hydrolase.

CONCLUSION

These findings suggested that genes related to cell wall metabolism and cuticle biosynthesis may play important roles in regulating grape berry cracking. Our results provide a reference for further studies on the molecular mechanism underlying fruit cracking.

Roles of transcription factor SQUAMOSA promoter binding protein-like gene family in papaya (Carica papaya) development and ripening

SQUAMOSA promoter binding protein-like (SPL) family plays vital regulatory roles in plant growth and development. The SPL family in climacteric fruit Carica papaya has not been reported. This study identified 14 papaya SPLs (CpSPL) from papaya genome and analyzed their sequence features, phylogeny, intron/exon structure, conserved motif, miR156-mediated posttranscriptional regulation, and expression patterns. 14 CpSPLs were clustered into 8 groups, and two distinct expression patterns were revealed for miR156-targeted and nontargeted CpSPLs in different tissues and fruit development stages. The expression changes of CpSPLs in ethephon and 1-MCP treated fruit during ripening suggested that the CpSPLs guided by CpmiR156 play crucial roles in ethylene signaling pathway. This study sheds light on the new function of SPL family in fruit development and ripening, providing insights on understanding evolutionary divergence of the members of SPL family among plant species.

Metabolome and proteome of ethylene-treated papayas reveal different pathways to volatile compounds biosynthesis

Papayas undergo fast postharvest changes triggered by the plant hormone ethylene. Some important pathways have been analyzed in limited studies (transcriptomics and targeted metabolomics); however, broad use of proteomics or untargeted metabolomics have not yet been used in papayas. In this study, two groups of green papayas (150 days after anthesis-physiological maturity for papayas) were treated with ethylene at different times (6 and 12 h) and their metabolic changes in fruit pulp were evaluated with untargeted metabolomics (general metabolites and volatile compounds) and proteomics. Polar metabolites exhibited distinct patterns, especially with regard to some amino and fatty acids during stimulated ripening. In particular, glutamate increased through a possible gamma aminobutyric acid (GABA) shunt and/or proteases activity. Moreover, the stimulated ripening altered the volatile compounds and the protein profiles. The results suggest that changes in membrane breakdown and the resulting oxidative processes could be responsible for volatile compound production, altering some sensorial qualities of papayas, such as pulp softening and the specific papaya linalool volatile compound increment. Thus, GABA levels could also be a strong biological marker for papaya development and ripening stages. This study applied two "omic" techniques that provided insight into how the plant hormone ethylene could influence papaya postharvest quality.

Karyopherin MoKap119-mediated nuclear import of cyclin-dependent kinase regulator MoCks1 is essential for Magnaporthe oryzae pathogenicity

Nuclear import of proteins relies on nuclear import receptors called importins/karyopherins (Kaps), whose functions were reported in yeasts, fungi, plants, and animal cells, including cell cycle control, morphogenesis, stress sensing/response, and also fungal pathogenecity. However, limited is known about the physiological function and regulatory mechanism of protein import in the rice-blast fungus Magnaporthe oryzae. Here, we identified an ortholog of β-importin in M. oryzae encoded by an ortholog of KAP119 gene. Functional characterisation of this gene via reverse genetics revealed that it is required for vegetative growth, conidiation, melanin pigmentation, and pathogenicity of M. oryzae. The mokap119Δ mutant was also defective in formation of appressorium-like structure from hyphal tips. By affinity assay and liquid chromatography-tandem mass spectrometry, we identified potential MoKap119-interacting proteins and further verified that MoKap119 interacts with the cyclin-dependent kinase subunit MoCks1 and mediates its nuclear import. Transcriptional profiling indicated that MoKap119 may regulate transcription of infection-related genes via MoCks1 regulation of MoSom1. Overall, our findings provide a novel insight into the regulatory mechanism of M. oryzae pathogenesis likely by MoKap119-mediated nuclear import of the cyclin-dependent kinase subunit MoCks1.

Fruit ripening: the role of hormones, cell wall modifications, and their relationship with pathogens

Fruits result from complex biological processes that begin soon after fertilization. Among these processes are cell division and expansion, accumulation of secondary metabolites, and an increase in carbohydrate biosynthesis. Later fruit ripening is accomplished by chlorophyll degradation and cell wall lysis. Fruit maturation is an essential step to optimize seed dispersal, and is controlled by a complex network of transcription factors and genetic regulators that are strongly influenced by phytohormones. Abscisic acid (ABA) and ethylene are the major regulators of ripening and senescence in both dry and fleshy fruits, as demonstrated by numerous ripening-defective mutants, effects of exogenous hormone application, and transcriptome analyses. While ethylene is the best characterized player in the final step of a fruit's life, ABA also has a key regulatory role, promoting ethylene production and acting as a stress-related hormone in response to drought and pathogen attack. In this review, we focus on the role of ABA and ethylene in relation to the interconnected biotic and abiotic phenomena that affect ripening and senescence. We integrate and discuss the most recent data available regarding these biological processes, which are crucial for post-harvest fruit conservation and for food safety.

Fast and Furious: Ethylene-Triggered Changes in the Metabolism of Papaya Fruit During Ripening

Papaya is a climacteric fleshy fruit characterized by fast ripening after harvest. During the relatively short postharvest period, papaya fruit undergoes several changes in metabolism that result in pulp softening and sweetening, as well as the development of a characteristic aroma. Since papaya is one of the most cultivated and appreciated tropical fruit crops worldwide, extensive research has been conducted to not only understand the formation of the quality and nutritional attributes of ripe fruit but also to develop methods for controlling the ripening process. However, most strategies to postpone papaya ripening, and therefore to increase shelf life, have failed to maintain fruit quality. Ethylene blockage precludes carotenoid biosynthesis, while cold storage can induce chilling injury and negatively affect the volatile profile of papaya. As a climacteric fruit, the fast ripening of papaya is triggered by ethylene biosynthesis. The generation of the climacteric ethylene positive feedback loop is elicited by the expression of a specific transcription factor that leads to an up-regulation of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) and ACC-oxidase (ACO) expression, triggering the system II ethylene biosynthesis. The ethylene burst occurs about 3 to 4 days after harvest and induces pectinase expression. The disassembling of the papaya cell wall appears to help in fruit sweetness, while glucose and fructose are also produced by acidic invertases. The increase in ethylene production also results in carotenoid accumulation due to the induction of cyclases and hydroxylases, leading to yellow and red/orange-colored pulp phenotypes. Moreover, the production of volatile terpene linalool, an important biological marker for papaya's sensorial quality, is also induced by ethylene. All these mentioned processes are related to papaya's sensorial and nutritional quality. We describe the understanding of ethylene-triggered events that influence papaya quality and nutritional traits, as these characteristics are a consequence of an accelerated metabolism during fruit ripening.

A qualitative proteome-wide lysine crotonylation profiling of papaya (Carica papaya L.)

Lysine crotonylation of histone proteins is a recently-identified post-translational modification with multiple cellular functions. However, no information about lysine crotonylation of non-histone proteins in fruit cells is available. Using high-resolution LC-MS/MS coupled with highly sensitive immune-affinity antibody analysis, a global crotonylation proteome analysis of papaya fruit (Carica papaya L.) was performed. In total, 2,120 proteins with 5,995 lysine crotonylation sites were discovered, among which eight conserved motifs were identified. Bioinformatic analysis linked crotonylated proteins to multiple metabolic pathways, including biosynthesis of antibiotics, carbon metabolism, biosynthesis of amino acids, and glycolysis. particularly, 40 crotonylated enzymes involved in various pathways of amino acid metabolism were identified, suggesting a potential conserved function for crotonylation in the regulation of amino acid metabolism. Numerous crotonylation sites were identified in proteins involved in the hormone signaling and cell wall-related pathways. Our comprehensive crotonylation proteome indicated diverse functions for lysine crotonylation in papaya.

A qualitative proteome-wide lysine crotonylation profiling of papaya (Carica papaya L.)

Lysine crotonylation of histone proteins is a recently-identified post-translational modification with multiple cellular functions. However, no information about lysine crotonylation of non-histone proteins in fruit cells is available. Using high-resolution LC-MS/MS coupled with highly sensitive immune-affinity antibody analysis, a global crotonylation proteome analysis of papaya fruit (Carica papaya L.) was performed. In total, 2,120 proteins with 5,995 lysine crotonylation sites were discovered, among which eight conserved motifs were identified. Bioinformatic analysis linked crotonylated proteins to multiple metabolic pathways, including biosynthesis of antibiotics, carbon metabolism, biosynthesis of amino acids, and glycolysis. particularly, 40 crotonylated enzymes involved in various pathways of amino acid metabolism were identified, suggesting a potential conserved function for crotonylation in the regulation of amino acid metabolism. Numerous crotonylation sites were identified in proteins involved in the hormone signaling and cell wall-related pathways. Our comprehensive crotonylation proteome indicated diverse functions for lysine crotonylation in papaya.

Analysis of β-Galactosidase During Fruit Development and Ripening in Two Different Texture Types of Apple Cultivars

β-galactosidase (β-Gal), one of the cell wall modifying enzymes, plays an important role in fruit ripening and softening. However, its role in apple fruit texture remains unclear. In this study, the role of β-Gal was analyzed in two apple cultivars, 'Fuji' and 'Qinguan,' which are characterized by different fruit texture types, during fruit development and ripening. The firmness and pectin content of the fruits rapidly decreased and were much lower in 'Fuji' than in 'Qinguan' from 105 days after full bloom (DAFB). Transmission electron microscopy showed that the pectin-rich middle lamella was substantially degraded from 105 to 180 DAFB in the two apple cultivars. However, the degradation was more severe in 'Fuji' than in 'Qinguan.' Subcellular localization analysis showed that the Mdβ-Gal1, Mdβ-Gal2, and Mdβ-Gal5 proteins were located in the cell wall. β-Gal activity continuously increased during all fruit developmental stages and was much higher in the mature fruits of 'Fuji' than in those of 'Qinguan,' indicating that pectin was degraded by β-Gal. Consistent with the enzyme activities, expression levels of β-Gal genes (Mdβ-Gal1, Mdβ-Gal2, and Mdβ-Gal5) showed only slight changes from 60 to 105 DAFB but then dramatically increased until fruit ripening, with higher values in 'Fuji' than in 'Qinguan.' Furthermore, we found that activities of deletion derivatives in the Mdβ-Gal2 promoter and transcript level of Mdβ-Gal2 were induced by the treatment with methyl jasmonate (MeJA) and ethylene (ETH) hormones. Two ETH and one MeJA hormone-responsive elements were identified by analyzing the promoter sequence. These results suggest that β-Gals, induced by ETH and MeJA, are involved in different fruit texture types of apple cultivars by influencing the degradation of pectin during the mature fruit stage.