Abscisic acid and stress induced by salt: Effect on the phenylpropanoid, L-ascorbic acid and abscisic acid metabolism of strawberry fruits.

Strawberry is one of the most popular fruits because of its sensorial and functional properties. However, strawberry crop is sensitive to salt stress conditions. Despite plants have plasticity, high salt concentrations induce molecular, biochemical, and physiological responses in plants. There is evidence that the abscisic acid (ABA) hormone acts as a signaling molecule under stress conditions; however, the molecular mechanisms involved in the synthesis and homeostasis of ABA and in the induction of phytochemical antioxidant compounds under stress conditions remain unclear. In this study, the effect of stress induced by NaCl (salt stress - SS), with or without the simultaneous application of ABA, on the ABA, phenylpropanoids and L-ascorbic acid (AsA) metabolisms were evaluated. The physiological aspects (Na, Cl and proline concentration, photosynthetic variables) were also studied. The results showed that salt stress increases the Na and Cl content in the leaves, affects photosynthetic variables and triggers the production of proline, pelargonidin-3-O-glucoside, total phenolic compounds and AsA content, alongside the upregulation of several genes from the phenylpropanoid and flavonoid pathways. These effects were accompanied by the induction of compounds and transcripts related to ABA biosynthesis, conjugation and catabolism. Otherwise, the exogenous application of ABA in salt stressed plants promotes a shift in gene expression and metabolism to mitigate the stress. Therefore, salt stress affects the metabolism of ABA, phenylpropanoids and AsA in strawberry increasing phytochemical composition which is strongly associated with an ABA-dependent mechanism.

Effects of flooding stress in tomato plants transformed with different levels of mitochondrial sHSP23 6 / Efeitos do estresse por alagamento em plantas de tomateiro transformada com diferentes níveis de sHSP23 6 mitocondrial

Abstract Soil flooding is an environmental stressor for crops that can affect physiological performance and reduce crop yields. Abiotic stressors cause changes in protein synthesis, modifying the levels of a series of proteins, especially the heat shock proteins (HSP), and these proteins can help protect the plants against abiotic stress. The objective of this study was to verify if tomato plants cv. Micro-Tom from different genotypes with varying expression levels of MT-sHSP23.6 (mitochondrial small heat shock proteins) have different responses physiological to flooding. Plants from three genotypes (untransformed, MT-sHSP23.6 sense expression levels and MT-sHSP23.6 antisense expression levels) were cultivated under controlled conditions. After 50 days, the plants were flooded for 14 days. After this period half of the plants from each genotype were allowed to recover. Chlorophyll fluorescence, gas exchange, chlorophyll index, leaf area and dry matter were evaluated. Flood stress affected the photosynthetic electron transport chain, which is related to inactivation of the oxygen-evolving complex, loss of connectivity among units in photosystem II, oxidation-reduction of the plastoquinone pool and activity of photosystem I. The genotype with MT-sHSP23.6 sense expression levels was less sensitive to stress from flooding.

Resumo O alagamento do solo é um estressor ambiental para as culturas e pode afetar o desempenho fisiológico e reduzir a produtividade das culturas. Estresses abióticos causam mudanças na síntese de proteínas, modificando os níveis de uma série de proteínas, em especial as proteínas de choque térmico (HSP) e essas proteínas são conhecidas por proteger as plantas contra estresses abióticos. O objetivo deste estudo foi verificar se as plantas do tomateiro cv. Micro-Tom de distintos genótipos com diferentes níveis de expressão da MT-sHSP23.6 (proteínas mitocondriais de choque térmico com pequena massa molecular), têm diferentes respostas fisiológicas ao alagamento. As plantas de três genótipos (não-transformado, transformado com orientação antisense e transformado com orientação sense para MT-sHSP23.6) foram cultivadas sob condições controladas. Após 50 dias as plantas foram alagadas durante 14 dias. Após esse período as plantas de cada genótipo foram recuperadas. Foram avaliados fluorescência da clorofila, trocas gasosas, índice de clorofila, área foliar e massa seca. O estresse por alagamento afetou a cadeia de transporte de elétrons da fotossíntese, que está relacionado à inativação do complexo de evolução do oxigênio, perda da conectividade entre as unidades do fotossistema II, de oxidação e redução do pool de plastoquinona e atividade do fotossistema I. O genótipo com orientação sense MT-sHSP23.6 foi menos sensível ao estresse por alagamento.

Effects of flooding stress in 'Micro-Tom' tomato plants transformed with different levels of mitochondrial sHSP23.6.

Soil flooding is an environmental stressor for crops that can affect physiological performance and reduce crop yields. Abiotic stressors cause changes in protein synthesis, modifying the levels of a series of proteins, especially the heat shock proteins (HSP), and these proteins can help protect the plants against abiotic stress. The objective of this study was to verify if tomato plants cv. Micro-Tom from different genotypes with varying expression levels of MT-sHSP23.6 (mitochondrial small heat shock proteins) have different responses physiological to flooding. Plants from three genotypes (untransformed, MT-sHSP23.6 sense expression levels and MT-sHSP23.6 antisense expression levels) were cultivated under controlled conditions. After 50 days, the plants were flooded for 14 days. After this period half of the plants from each genotype were allowed to recover. Chlorophyll fluorescence, gas exchange, chlorophyll index, leaf area and dry matter were evaluated. Flood stress affected the photosynthetic electron transport chain, which is related to inactivation of the oxygen-evolving complex, loss of connectivity among units in photosystem II, oxidation-reduction of the plastoquinone pool and activity of photosystem I. The genotype with MT-sHSP23.6 sense expression levels was less sensitive to stress from flooding.

Expression profile of rice Hsp genes under anoxic stress.

Although flooding is one of the most important environmental stresses worldwide, not all plant species are intolerant to its effects. Species from semi-aquatic environments, such as rice, have the capacity to cope with flooding stress. Heat-shock proteins (Hsps) are thought to contribute to cellular homeostasis under both optimal and adverse growth conditions. Studies of gene expression in plants exposed to low levels of oxygen revealed the up-regulation of Hsp genes. However, it is not clear whether Hsp genes are transcribed as a function of tolerance or whether they represent a response to anoxic stress. Therefore, the accumulation of Hsp gene transcripts was investigated in two different cultivars, "Nipponbare" (flooding tolerant) and "IPSL 2070" (flooding sensitive), subjected to anoxic stress. Fifteen-day-old rice root seedlings from both cultivars were used. Four different treatments were performed: no anoxia (control); 24-h anoxia; 48-h anoxia; and 72-h anoxia. Anoxic stress was confirmed by the increased gene expression of alcohol dehydrogenase. The data obtained showed that both rice cultivars ("Nipponbare" and "IPSL 2070") accumulated Hsp gene transcripts under anoxic stress; however, the majority of the Hsp genes evaluated were responsive to anoxic stress in "IPSL 2070" (flooding sensitive), whereas in "Nipponbare" (flooding tolerant), only six genes were highly up-regulated. This suggests that although Hsps have an important role in the response to anoxia, they are not the major cause of tolerance.

Immunocytolocalization of 1-aminocyclopropane-1-carboxylic acid oxidase in tomato and apple fruit.

The subcellular localization of 1-aminocyclopropane-1-carboxylic acid oxidase (ACC oxidase), an enzyme involved in the biosynthesis of ethylene, has been studied in ripening fruits of tomato (Lycopersicum esculentum Mill.). Two types of antibody have been raised against (i) a synthetic peptide derived from the reconstructed pTOM13 clone (pRC13), a tomato cDNA encoding ACC oxidase, and considered as a suitable epitope by secondary-structure predictions; and (ii) a fusion protein overproduced in Escherichia coli expressing the pRC13 cDNA. Immunoblot analysis showed that, when purified by antigen affinity chromatography, both types of antibody recognized a single band corresponding to ACC oxidase. Superimposition of Calcofluor white with immunofluorescence labeling, analysed by optical microscopy, indicated that ACC oxidase is located at the cell wall in the pericarp of breaker tomato and climacteric apple (Malus x domestica Borkh.) fruit. The apoplasmic location of the enzyme was also demonstrated by the observation of immunogold-labeled antibodies in this region by both optical and electron microscopy. Transgenic tomato fruits in which ACC-oxidase gene expression was inhibited by an antisense gene exhibited a considerable reduction of labeling. Immunocytological controls made with pre-immune serum or with antibodies pre-absorbed on their corresponding antigens gave no staining. The discrepancy between these findings and the targeting of the protein predicted from sequences of ACC-oxidase cDNA clones isolated so far is discussed.

Purification, properties and partial amino-acid sequence of 1-aminocyclopropane-1-carboxylic acid oxidase from apple fruits.

The enzyme which converts 1-aminocyclopropane-1-carboxylic acid (ACC) into ethylene, ACC oxidase, has been isolated from apple fruits (Malus x domestica Borkh. cv. Golden Delicious), and for the first time stabilized in vitro by 1,10-phenanthroline and purified 170-fold to homogeneity in a five-step procedure. The sodium dodecyl sulfate-denatured and native proteins have similar molecular weights (approx. 40 kDa) indicating that the enzyme is active in its monomeric form. Antibodies raised against a recombinant ACC oxidase over-produced in Escherichia coli from a tomato cDNA recognise the apple-fruit enzyme with high specificity in both crude extracts and purified form. Glycosylation appears to be absent because of (i) the lack of reactivity towards a mixture of seven different biotinylated lectins and (ii) the absence of N-linked substitution at a potential glycosylation site, in a sequenced peptide. Phenylhydrazine and 2-methyl-1-2-dipyridyl propane do not inhibit activity, indicating that ACC oxidase is not a prosthetic-heme iron protein. The partial amino-acid sequence of the native protein has strong homology to the predicted protein of a tomato fruit cDNA demonstrated to encode ACC oxidase.

Hereditary adenomatosis of the colon and rectum: clinical features of eight families from northern Italy.

Adenomatosis coli (or familial polyposis of the large bowel) and related syndromes are relatively rare diseases characterized by an autosomal dominant mode of inheritance. In these diseases, the entire colorectal mucosa is covered by hundreds (often innumerable) polyps of various dimensions. In addition, several extracolonic abnormalities have been reported. In the present study, we describe the clinical features of eight families from northern Italy fulfilling the diagnostic criteria of adenomatosis coli. Information was available on 123 unaffected and 30 affected family members. The most relevant findings of the study can be summarized as follows. 1) Gene frequency was calculated to be between 1:7,300 and 1:19,000. Segregation ratio in affected branches was 0.57, with a gene penetrance of nearly 60% and a male:female ratio of 1.73. 2) Extracolonic manifestations were present in all families and in 15 of 30 affected patients, the most frequent being cutaneous cysts and retinal lesions. No case fulfilling the classical criteria of Gardner syndrome was observed. 3) When the diagnosis of adenomatosis followed the appearance of symptoms, colorectal cancer had usually already developed, whereas no malignant changes were observed in individuals diagnosed in the asymptomatic stage. When colectomy with ileorectal anastomosis was the treatment of choice, polyps tended to recur in the rectal stump, and long-term endoscopic follow-up was necessary. In conclusion, adenomatosis coli may account for a definite proportion of colorectal neoplasms observed in the general population. Taking into consideration the genetic base of the disease, it follows that individuals at risk should be closely monitored for several years. Moreover, clinical investigations should not be limited to the large bowel, but should be extended to the skin, upper digestive tract, fundus oculi, bones, and probably other organs.