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Seven-day old wheat seedlings (Triticum aestivum L. cv. MEC) were incubated in small jars, fluxed with gas mixtures of nitrogen-oxygen (oxygen concentrations 0, 0.3, 1, 2.5, 10%) for up to 48 h. Effects of anoxia and hypoxia on ethylene evolution and ethylene-forming enzyme (EFE) activity were determined 1 h after the plants had been transferred to air, respectively. 1-aminocyclopropane-1-carboxylic acid (ACC) content was measured immediately after treatments. Results showed that the ethylene production is differently affected by oxygen deprivation in roots and leaves. The effects are more closely related to ACC accumulation than to the EFE activity. In leaves, ethylene evolution is almost unaffected by oxygen concentrations above ca 1%. [ABSTRACT FROM AUTHOR]

In light of ongoing climate changes in wine-growing regions, the selection of drought-tolerant rootstocks is becoming a crucial factor for developing a sustainable viticulture. In this study, M, a new rootstock genotype that shows tolerance to drought, was compared from a genomic and transcriptomic point of view with the less drought-tolerant genotype 101.14. The root and leaf transcriptome of both 101.14 and the M4 rootstock genotype was analysed, following exposure to progressive drought conditions. Multifactorial analyses indicated that stress treatment represents the main factor driving differential gene expression in roots, whereas in leaves the genotype is the prominent factor. Upon stress, M4 roots and leaves showed a higher induction of resveratrol and flavonoid biosynthetic genes, respectively. The higher expression of VvSTS genes in M, confirmed by the accumulation of higher levels of resveratrol in M4 roots compared with 101.1, was coupled to an up-regulation of several VvWRKY transcription factors. Interestingly, VvSTS promoter analyses performed on both the resequenced genomes highlighted a significantly higher number of W-BOX elements in the tolerant genotype. It is proposed that the elevated synthesis of resveratrol in M4 roots upon water stress could enhance the plant's ability to cope with the oxidative stress usually associated with water deficit. [ABSTRACT FROM AUTHOR]

Apple (Malus domestica) fruitlet abscission represents an interesting model system to study the early phases of the shedding process, during which major transcriptomic changes and metabolic rearrangements occur within the fruit. In apple, the drop of fruits at different positions within the cluster can be selectively magnified through chemical thinners, such as benzyladenine and metamitron, acting as abscission enhancers. In this study, different abscission potentials were obtained within the apple fruitlet population by means of the above-cited thinners. A metabolomic study was conducted on the volatile organic compounds emitted by abscising fruitlets, allowing for identification of isoprene as an early marker of abscission induction. A strong correlation was also observed between isoprene production and abscisic acid (ABA) levels in the fruit cortex, which were shown to increase in abscising fruitlets with respect to nonabscising ones. Transcriptomic evidence indicated that abscission-related ABA is biologically active, and its increased biosynthesis is associated with the induction of a specific ABA-responsive 9-cis-epoxycarotenoid dioxygenase gene. According to a hypothetical model, ABA may transiently cooperate with other hormones and secondary messengers in the generation of an intrafruit signal leading to the downstream activation of the abscission zone. The shedding process therefore appears to be triggered by multiple interdependent pathways, whose fine regulation, exerted within a very short temporal window by both endogenous and exogenous factors, determines the final destiny of the fruitlets. [ABSTRACT FROM AUTHOR]

Abstract: The flavor and taste of fruits are often determined by terpenes. We identified three cDNAs encoding putative terpene synthases from olive fruits of cv. Frantoio and Grignano. Heterologous expression in a bacterial system demonstrated that one of the terpene synthases, OeGES1, was an active monoterpene synthase that converted geranyl diphosphate to the monoterpene alcohol geraniol. The transcript accumulation pattern of this gene showed a peak during fruit ripening in both genotypes, indicating that the enzyme may be involved in the production of monoterpene flavor compounds in olive fruit. Although the putative terpene synthases OeTPS2 and OeTPS3 clustered with α-farnesene synthases and angiosperm monoterpene synthases, no detectable in vitro activity was found after expression in a bacterial system. Nevertheless, their transcripts sharply accumulated during fruit ripening starting from véraison. [Copyright &y& Elsevier]

transcriptome analysis was applied on two peach ( Prunus persica L.) cultivars with different sensitivity to low temperature regimes to identify genes that might be involved in tolerance to extended low temperature storage. Peach fruit from 'Morettini No2' to 'Royal Glory', cultivars sensitive and tolerant to chilling injury (CI), respectively, were harvested at commercial maturity stage and allowed to ripen at room temperature (shelf-life, 25°C) or subjected to 4 and 6 weeks of cold storage (0°C, 95% R.H.) followed by ripening at room temperature. The use of μPEACH 1.0 microarray platform identified a number of genes that were differentially expressed in 'Morettini No2' and 'Royal Glory' fruit after the extended storage period. Based on their possible involvement in physiological processes related to cold storage and on their differential expression pattern, two heat shock proteins, a β-D-xylosidase, an expansin, a dehydrin and a pathogenesis-related (PR) protein were further selected for detailed analysis via RNA blot analysis. It is suggested that β- d-xylosidase and PR-4B precursor genes could be related to the different tolerance to CI observed in the two peach cultivars since generally higher expression levels were observed in cv. 'Royal Glory', the tolerant one. These two genes could play a role in peach tolerance to chilling injury. [ABSTRACT FROM AUTHOR]

Volatile organic compounds of extra virgin olive oils obtained from the local Italian cultivar Grignano were measured by proton transfer reaction-mass spectrometry (PTR-MS). Oils were extracted by olives harvested at different ripening stages across veraison, performing each extraction step and the whole extraction process in nitrogen atmosphere to observe the changes in the volatile profiles of the oils. Principal component analysis carried out on the full spectral signature of the PTR-MS measurements showed that the stage of ripening has a stronger effect on the global definition of volatile profiles than the use of nitrogen during oil extraction. The fingerprint-like chemical information provided by the spectra were used to construct a heat map, which allowed the dynamical representation of the multivariate nature of mass evolution during the ripening process. This provided the first evidence that some groups of volatile organic compounds displayed a time course of regulation with coordinated increasing or decreasing trends in association with specific stages of fruit ripening. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Apple (Malus x domestica) represents an interesting model tree crop for studying fruit abscission. The physiological fruitlet drop occurring in this species can be easily magnified by using thinning chemicals, such as benzyladenine (BA), to obtain fruits with improved quality and marketability. Despite the economic importance of this process, the molecular determinants of apple fruitlet abscission are still unknown. In this research, BA was used to obtain fruitlet populations with different abscission potentials to be analyzed by means of a newly released 30K oligonucleotide microarray. RNAs were extracted from cortex and seed of apple fruitlets sampled over a 4-d time course, during which BA triggers fruit drop, and used for nlicroarray hybridization. Transcriptomic profiles of persisting and abscising fruitlets were tested for statistical association with abscission potential, allowing us to identify molecular signatures strictly related to fruit destiny. A hypothetical model for apple fruitlet abscission was obtained by putting together available transcriptomic and metabolomic data. According to this model, BA treatment would establish a nutritional stress within the tree that is primarily perceived by the fruitlet cortex whose growth is blocked by resembling the ovary growth inhibition found in other species. In weaker fruits, this stress is soon visible also at the seed level, likely transduced via reactive oxygen species/sugar and hormones signaling cross talk, and followed by a block of embryogenesis and the consequent activation of the abscission zone. [ABSTRACT FROM AUTHOR]

Background: Field observations and a few physiological studies have demonstrated that peach embryogenesis and fruit development are tightly coupled. In fact, attempts to stimulate parthenocarpic fruit development by means of external tools have failed. Moreover, physiological disturbances during early embryo development lead to seed abortion and fruitlet abscission. Later in embryo development, the interactions between seed and fruit development become less strict. As there is limited genetic and molecular information about seed-pericarp crosstalk and development in peach, a massive gene approach based on the use of the μPEACH 1.0 array platform and quantitative real time RT-PCR (qRT-PCR) was used to study this process. Results: A comparative analysis of the transcription profiles conducted in seed and mesocarp (cv Fantasia) throughout different developmental stages (S1, S2, S3 and S4) evidenced that 455 genes are differentially expressed in seed and fruit. Among differentially expressed genes some were validated as markers in two subsequent years and in three different genotypes. Seed markers were a LTP1 (lipid transfer protein), a PR (pathogenesis-related) protein, a prunin and LEA (Late Embryogenesis Abundant) protein, for S1, S2, S3 and S4, respectively. Mesocarp markers were a RD22-like protein, a serin-carboxypeptidase, a senescence related protein and an Aux/IAA, for S1, S2, S3 and S4, respectively. The microarray data, analyzed by using the HORMONOMETER platform, allowed the identification of hormoneresponsive genes, some of them putatively involved in seed-pericarp crosstalk. Results indicated that auxin, cytokinins, and gibberellins are good candidates, acting either directly (auxin) or indirectly as signals during early development, when the cross-talk is more active and vital for fruit set, whereas abscisic acid and ethylene may be involved later on. Conclusions: In this research, genes were identified marking different phases of seed and mesocarp development. The selected genes behaved as good seed markers, while for mesocarp their reliability appeared to be dependent upon developmental and ripening traits. Regarding the cross-talk between seed and pericarp, possible candidate signals were identified among hormones. Further investigations relying upon the availability of whole genome platforms will allow the enrichment of a marker genes repertoire and the elucidation of players other than hormones that are involved in seed-pericarp cross-talk (i.e. hormone peptides and microRNAs). [ABSTRACT FROM AUTHOR]

Abstract: Apple Malus X domestica fruitlet abscission is preceded by a stimulation of ethylene biosynthesis and a gain in sensitivity to the hormone. This phase was studied by a differential screening carried out by cDNA-AFLP in abscising (AF) and non-abscising (NAF) fruitlet populations. Fifty-three primer combinations allowed for the isolation of 131, 66 and 30 differentially expressed bands from cortex, peduncle and seed, respectively. All sequences were then classified as up- or down-regulated by comparing the profile in AFs and NAFs. Almost all of these sequences showed significant homology to genes encoding proteins with known or putative function. The gene ontology analysis of the TDFs isolated indicated a deep change in metabolism, plastid and hormonal status, especially auxin. Furthermore, some common elements between abscission and senescence were identified. The isolation of the full length of one of these TDFs allowed for the identification of a gene encoding an auxin hydrogen symporter (MdAHS). Bioinformatic analysis indicated that the deduced protein shares some features with other auxin efflux carriers, which include PINs. Nevertheless the 3D structure pointed out substantial differences and a conformation largely dissimilar from canonical ion transporters. The expression analysis demonstrated that this gene is regulated by light and development but not affected by ethylene or auxin. [Copyright &y& Elsevier]

Abstract: Aspergillus carbonarius is responsible for the majority of mycotoxin contaminations in grapes and its derivatives. Most of A. carbonarius strains are ochratoxin A (OTA) producers, even though at very different levels. This broad variability was used to identify genes whose expression is linked with the ability of producing OTA. A cDNA-AFLP differential display screening was performed in two strains of A. carbonarius, antagonists for the ability of producing OTA, allowing the identification of 119 differentially expressed sequences putatively involved in the regulation of OTA biosynthesis. A likely connection was pointed out between the biosynthesis of the toxin, vegetative growth and sexual/asexual developmental progression, along with common signalling pathways involving G protein and Ca2+/calmodulin dependent phosphorylation and dephoshorylation cascades. [Copyright &y& Elsevier]

Background: After 10-year-use of AFLP (Amplified Fragment Length Polymorphism) technology for DNA fingerprinting and mRNA profiling, large repertories of genome- and transcriptome-derived sequences are available in public databases for model, crop and tree species. AFLP marker systems have been and are being extensively exploited for genome scanning and gene mapping, as well as cDNA-AFLP for transcriptome profiling and differentially expressed gene cloning. The evaluation, annotation and classification of genomic markers and expressed transcripts would be of great utility for both functional genomics and systems biology research in plants. This may be achieved by means of the Gene Ontology (GO), consisting in three structured vocabularies (i.e. ontologies) describing genes, transcripts and proteins of any organism in terms of their associated cellular component, biological process and molecular function in a species-independent manner. In this paper, the functional annotation of about 8,000 AFLP-derived ESTs retrieved in the NCBI databases was carried out by using GO terminology. Results: Descriptive statistics on the type, size and nature of gene sequences obtained by means of AFLP technology were calculated. The gene products associated with mRNA transcripts were then classified according to the three main GO vocabularies. A comparison of the functional content of cDNA-AFLP records was also performed by splitting the sequence dataset into monocots and dicots and by comparing them to all annotated ESTs of Arabidopsis and rice, respectively. On the whole, the statistical parameters adopted for the in silico AFLP-derived transcriptome-anchored sequence analysis proved to be critical for obtaining reliable GO results. Such an exhaustive annotation may offer a suitable platform for functional genomics, particularly useful in non-model species. Conclusion: Reliable GO annotations of AFLP-derived sequences can be gathered through the optimization of the experimental steps and the statistical parameters adopted. The Blast2GO software was shown to represent a comprehensive bioinformatics solution for an annotation-based functional analysis. According to the whole set of GO annotations, the AFLP technology generates thorough information for angiosperm gene products and shares common features across angiosperm species and families. The utility of this technology for structural and functional genomics in plants can be implemented by serial annotation analyses of genome-anchored fragments and organ/tissue-specific repertories of transcriptome-derived fragments. [ABSTRACT FROM AUTHOR]

The influence of internal and external factors such as tree fruit load and elevation on ethylene biosynthesis and action was assessed during apple fruit development and ripening. Ethylene biosynthesis, as well as transcript accumulation of the hormone biosynthetic enzymes ( MdACS1 and MdACO1), receptors ( MdETR1 and MdERS1) and an element of the transduction pathway ( MdCTR1), were evaluated in apples borne by trees with high (HL) and low (LL) fruit load. Orchards were located in two localities differing in elevation and season day degree sum. These parameters significantly affected the date of bloom and commercial harvest, and the length of the fruit developmental cycle. Trees from the low elevation (LE) bloomed and the fruit ripened earlier than those from the high elevation (HE), displaying also a shortened fruit developmental cycle. Dynamics of ethylene evolution was apparently not affected by elevation. The onset of ethylene evolution started 130 days after bloom (DAB) at both elevations. During early ripening, fruits from LL trees produced significantly more ethylene than those from HL trees. Expression analysis of MdACS1, MdACO1 and MdERS1 indicated that the transcript accumulation well correlated with ethylene evolution. MdCTR1 was expressed at constant level throughout fruit growth and development up to 130 DAB, thereafter, the transcript accumulation decreased up to commercial harvest, concurrently with the onset of ethylene evolution. [ABSTRACT FROM AUTHOR]

Abstract: The full-length cDNAs of Pp-LTP1 and Pp-LTP2, two members of the lipid transfer protein (LTP) multigene family in peach (Prunus persica L. Batsch), have been isolated along with the proximal promoter and the complete genomic sequence of Pp-LTP1. As observed in other plant species, Pp-LTP1 is organized in two exons and, according to the deduced amino acid sequence of the secreted protein, it encodes the 9kDa allergenic protein Pru p 3. Pp-LTP1 transcripts and Pru p 3 protein markedly accumulate in epicarp of ripe fruit in all of the peach and nectarine varieties examined (including ‘Royal Gem’) with the exception of ‘Rita Star’ that shows weak specific mRNA hybridization signal and no Pru p 3 accumulation. SDS-PAGE clearly displays a different banding pattern in correspondence of 9kDa between ‘Rita Star’ and ‘Royal Gem’. In immunoblotting analysis, performed using sera of eight LTP pos+ patients, a strong band is present when using ‘Royal Gem’ epicarp extract but not in the case of ‘Rita Star’. According to these data, ‘Rita Star’ appears an interesting model to better elucidate the role of LTP in fruit development and allergenic reactions. [Copyright &y& Elsevier]

Abstract: In this paper, ethylene production, ACC quantification, and the determination of ACC-oxidase (ACO) activity and the transcript levels PdACS1, PdACO1, and PdACO2, have been evaluated in different parts of developing flowers (sepals, petals, stamens, and pistils) and fruits (epicarp, mesocarp, and seed) of damson plum (Prunus domestica L. subsp. Syriaca), which is a drupe. The fertilized pistil was the only floral organ to register net ethylene production. PdACS1 mRNA was detected exclusively in the stamen. Regarding PdACO1 and PdACO2 transcription, at pre-anthesis, anthesis, and post-anthesis, it was found that: (a) both genes were expressed in all studied floral organs, but accumulation of PdACO1 transcripts was consistently higher; (b) anthesis provoked a sharp accumulation of PdACO1 in sepals, petals, and stamens, while in the pistil no changes occurred; (c) an increase of PdACO2 transcription occurred in sepals concomitantly with anthesis; (d) pollination appeared to activate the transcription of PdACO1 in the pistil. The whole fruit of this plum produced ethylene only at the beginning of S1 and in S4 (climacteric), while the seed produced it at the end of the S1 and throughout S2, when a great richness in ACC and high ACO activity occurred. PdACS1 expression was detectable in the whole fruit at the beginning of development and in the epicarp and mesocarp during ripening. No expression of PdACS1 has been detected in isolated seeds. Even though the transcript for PdACO2 was temporal and spatially absent in fruit development, mRNA levels of PdACO1 notably changed. In the seed, the higher transcriptional activity of PdACO1 appeared at the end of phase S1. The greatest amounts of ACC were registered in the ripening mesocarp and epicarp. Whereas PdACO1 mRNA was detected in the mesocarp at the middle of S1, during the breaker stage (S3), and at the end of the climacteric phase (S4), in epicarp the expression occurred only in S4 stage. These results clearly demonstrate that the seed actively participates in ethylene production during the first phase of damson plum development. [Copyright &y& Elsevier]

Abstract: The transition from pre-climacteric to climacteric phase is a critical step during fruit development. A holistic approach to study this transition has been undertaken using the first available peach microarray (μPEACH1.0) containing about 4800 oligonucleotide probes corresponding to a set of unigenes most of them expressed during the last stages of fruit development. Microarray hybridizations indicated that among the genes present in the microarray slide, 267 and 109 genes are up- and down-regulated, respectively. Genes have been classified according to the TAIR Gene Ontology into three main categories based on cellular localization, molecular function and biological process. Considering the cellular localization, the most significant up- and down-regulated gene products belong to cell wall and chloroplast compartments. Within the molecular function and biological process categories, a dramatic up-regulation has been detected for genes encoding transcription factors and enzymes involved in ethylene biosynthesis and action. A new member of ETR peach family (Pp-ETR2) has been characterized: this gene shows high similarity to Arabidopsis EIN4, tomato Le-ETR4, and strawberry Fa-ETR2. Transition from S3 to S4 is paralleled by changes in expression of 19 genes encoding transcription factors (TFs) belonging to several families including MADS-box, AUX/IAA, bZIP, bHLH, HD, and Myb. Differential expression of genes involved in specific quality traits has also been observed: besides confirming previous data on cell wall-related gene expression, a new pectin-methyl esterase and two new expansins have been identified. Several genes encoding enzymes acting in the isoprenoid biosynthetic pathway appeared to be strongly induced at S3/S4 transition. Among those involved in carotenoid biosynthesis we found also a β-carotene hydroxylase, responsible for the formation of β-cryptoxanthin, the most abundant carotenoid of ripe yellow peaches. [Copyright &y& Elsevier]

Abscission was studied in immature apple fruits (cv. Golden Delicious) during the physiological drop. Fruitlet populations, characterized by different abscission potential, were analysed. Non-abscising fruitlets (NAF) were obtained from central flowers borne in clusters where all the lateral flowers had been removed at bloom while abscising fruitlets (AF) were derived from lateral fruitlets of trees sprayed with benzylaminopurine (BAP) at 200 ppm, 17 d after petal fall (APF), when the fruit cross diameter was about 10–12 mm. Fruit shedding, monitored at the end of the June drop, was significantly different in the two populations, being less than 10%, and more than 90%, in NAF and AF, respectively. In AF, fruit drop peaked around 33 d after petal fall (APF) and was preceded by an increase in ethylene around 20 d APF. Transcript analysis was performed from 17–24 d APF, since preliminary experiments pointed out that major changes in expression of abscission related genes occurred within this period. Transcript accumulation of genes involved in ethylene biosynthesis (MdACS5B and MdACO) and action (MdERS1, MdETR1, and MdCTR1) was studied in the seed, cortex, peduncle, and abscission zone (AZ) of the two fruit populations. MdACS5B and MdACO transcripts accumulated along the experimental period in AF population, even though at a different magnitude, while ethylene evolution declined after peaking at day three. MdETR1, MdERS1, and MdCTR1 expression patterns depended on tissue and/or population. The ERS/ETR ratio was higher in AF than in NAF populations. Overall results pointed out that apple fruitlet drop is preceded by a stimulation of ethylene biosynthesis and a gain in sensitivity to the hormone. [ABSTRACT FROM PUBLISHER]

To investigate the transcriptional regulation of two 1-aminocyclopropane-1-carboxylate (ACC) oxidase (ACO) genes of peach, chimeric fusions between β-glucuronidase (GUS) reporter gene, and Pp-ACO1 and Pp-ACO2 promoters have been constructed and introduced in tomato (cv Microtom). Pp-ACO1 promoter is able to induce in transgenic tomato plants the same pattern of expression observed in peach. In fact, Pp-ACO1–GUS activity was localized in leaf blade, ovary, leaf and fruit abscission zones and pericarp, and it is up-regulated by propylene and wounding. A gradient of transcript accumulation has been observed in ripening fruit tissues: in tomato it decreased moving from the inner to the outer pericarp, while in peach the opposite occurred. This different behavior could be related to the fruit type (berry vs. drupe). In order to identify cis-acting element involved in ethylene induction of Pp-ACO1, portions of its promoter fused with the GUS gene have been constructed and used in peach fruit transient activity assay. The deletion analysis has shown that a region located between −716 and −346 bp, containing an ethylene-responsive element (ERE), is responsible for the higher stimulation by the gas. In addition, two auxin-responsive elements (AUXre), probably responsible for the auxin suppression of the propylene induction of Pp-ACO1 gene expression, are present upstream from EREs. Pp-ACO2 promoter is able to drive the expression in vascular bundles of immature and ripe fruit, senescent leaf blade, and in fruit and leaf abscission zones. In peach, Pp-ACO2 mRNA is detected only in immature fruit, epicotyl and root of seedling. This discrepancy might be imputed to a lesser stability and translation of Pp-ACO2 mRNA in comparison to that of chimeric one. [Copyright &y& Elsevier]

Two peach genes homologous to the Arabidopsis ethylene receptor genes ETR1 and ERS1, named Pp‐ETR1 and Pp‐ERS1 respectively, have been isolated and characterized. Pp‐ETR1 and Pp‐ERS1 are conserved in terms of exon numbers and intron positions, although the first and fifth introns of Pp‐ETR1 have an unusual length. In addition, two putative polyadenylation sites, that may cause an incomplete splicing at the 3′ terminus, are present in the fifth intron. A motif of 28 nt, which shows high homology with ethylene responsive elements found in promoters of genes up‐regulated by ethylene, is present in the promoter region of Pp‐ERS1. Expression analysis, carried out by quantitative RT‐PCR, was performed during fruit development and ripening, and leaf and fruitlet abscission. The level of Pp‐ETR1 transcripts remained unchanged in all the tissues and developmental stages examined, whereas Pp‐ERS1 mRNA abundance increased in ripening mesocarp, in leaf and fruitlet activated abscission zones, and following propylene application. 1‐methylcyclopropene (1‐MCP), an inhibitor of ethylene action, did not affect Pp‐ETR1 transcription, while it down‐regulated Pp‐ERS1. A rise in ethylene evolution, accompanied by an increase of Pp‐ERS1 transcript accumulation occurred within 24 h from the end of 1‐MCP treatment. These results indicate that Pp‐ERS1 might play a role in abscission and ripening. [ABSTRACT FROM PUBLISHER]

We report the isolation of a new peach gene, Pp-MLP1, that shows significant similarity to a family of fruit- and flower-specific genes, designated as major latex protein (MLP) homologues. Transcript of Pp-MLP1 highly accumulated in cells of fruit pedicel, similar to lacticifers, adjacent to the abscission zone (non-abscission zone) and, to a lesser extent, in epicotyls, stems and roots, while no accumulation was detected in leaves. In contrast to the MLP homologues isolated so far, the Pp-MLP1 transcript was detected during fruit cells expansion, though its expression appeared unrelated to fruit ripening. Propylene treatment caused a decrease in mRNA accumulation of Pp-MLP1 in all tested tissues. The function of Pp-MLP1, as with all previously described MLP homologues, is unknown. MLPs are associated with fruit and flower development in addition to plant pathogenesis responses. Expression in tissues associated with abscission would be consistent with a role in implementing this aspect of floral development or possibly protective responses to plant pathogens which may infect post-abscission wounds. In addition, the high similarity between proteins encoding by Pp-MLP1 and Csf2, an MLP gene associated with the early development of cucumber fruit, could suggest an alternative developmental role such as cell and tissue expansion. [Copyright &y& Elsevier]

Ethylene‐responsive genes from peach (Prunus persica, L. Batsch) were isolated by differential screening of a cDNA library constructed from abscission zones in which cell separation had been evoked by treatment with the ethylene analogue propylene. DNA and deduced protein sequences of four selected clones, termed Prunus persica Abscission zone (PpAz), revealed homology to thaumatin‐like proteins (PpAz8 and PpAz44), to proteins belonging to the PR4 class of pathogenesis‐related (PR) proteins (PpAz89), and to fungal and plant β‐d‐xylosidases (PpAz152). Expression analyses conducted on embrioctomized and CEPA‐treated fruitlets as well as on fruit explants have shown that PpAz8, PpAz44 and PpAz89 are preferentially transcribed in the cells of the fruit abscission zone rather than in the non‐zone tissues. The PpAz152 transcript showed a different accumulation pattern being consistently and promptly induced by wounding and only slightly stimulated by propylene. By contrast, a complex pattern of transcript accumulation was found for the four genes in response to the wounding of leaves and during organ development and senescence. Based on this evidence, the existence of multiple regulatory pathways underlying the differential expression of the four PpAz genes in the different tissues and physiological processes is hypothesized. [ABSTRACT FROM PUBLISHER]

The characterization and expression of PP-ACO1 and PP-ACO2, two members of the peach 1-aminocyclopropane-1-carboxylate (ACC) oxidase (ACO) gene family, are reported. PP-ACO1 is organized in 4 exons interrupted by 3 introns, whereas PP-ACO2 has only 2 of the 3 introns present in PP-ACO1. Comparison of the deduced amino acid sequences of PP-ACO1 and PP-ACO2 reveals a 77.7% identity. PP-ACO1 and PP-ACO2 show highest degree of similarity with petunia (PH-ACO3; 84.1%) and apple (85.4%) ACO genes, respectively. PP-ACO1 is expressed in flowers, fruitlet abscission zones, mesocarp and in young fully expanded leaves. PP-ACO1 transcript accumulation strongly increases during fruitlet abscission, in ripe mesocarp and senescing leaves, and is enhanced by propylene. PP-ACO2 mRNA accumulation is detected in fruits only during early development and is unaffected by propylene treatment. Both ACO genes are expressed in epicotyl and roots of growing seedlings, although a stronger accumulation of PP-ACO2 mRNA is observed. [ABSTRACT FROM AUTHOR]

During peach (Prunus persica [L.] Batsch) fruit development and ripening the cell wall undergoes several structural and biochemical changes driven by several hydrolases. Among these, the endo-β-1,4-D-glucanase (EGase, EC 3.2.1.4), or cellulase, may play a crucial role. Involvement of EGase throughout development and ripening of the fruit of cv. Redhaven was assessed by monitoring enzyme activity, specific polypeptide accumulation and gene transcription. During the four stages of growth EGase activity was high during S1 and in the early S2, declined during S3, and increased with the onset of ripening (S4). Two isoforms with isolectric points of 6.5 and 9.5 were identified. The pI 6.5 EGase was the only form present during the early stages of growth. whereas the pI 9.5 EGase was most abundant during ripening. The same isoforms were present in leaf and fruit abscission zones. The antibody raised against the pI 9.5 EGase, purified from leaf abscission zones, cross-reacted with a protein of 54 kDa. A cDNA clone of 753 bp encoding peach EGase was obtained by RT-PCR. EGase transcripts, detectable only after amplification of total RNA by RT-PCR, were observed during S1, and at the preclimacteric and climacteric stages. However, the strongest hybridisation occurred at ripening, in correspondence with the maximal enzyme activity and polypeptide accumulation, which took place before the ethylene climacteric and in the early stage of flesh softening. Propylene treatments reduced EGase activity during the early stage of fruit growth but dramatically enhanced enzyme activity and the related transcript accumulation at ripening, and accelerated the loss of firmness. In fruit treated with 2,5-norbornadiene the softening process was strongly inhibited and the rise in EGase transcripts and activity did not take place. The results point to the EGases being involved in early fruit growth and the initial phases of softening. The presence of two isoforms and the dual effect of propylene on enzyme activity suggest that different EGase genes operate during the early and late developmental stages in peach fruit. [ABSTRACT FROM AUTHOR]