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Instituto de Biologia Unicamp






ABSTRACTA IB (2) - 1999

ERRATA - 1998

P001-98 Chilling induced chnges in membrane fluidity and antioxidant enzyme activities in Coffea arabica roots

Queiroz CGS, Alonso A, Mares-Guia M, Magalhães AC*

Biologia Plantarum 41: 403-413, 1998
*Fone: 788-7696; 788-7032

P003-98 Tobacco mosaic virus disasembly by high hydrostatic pressure in combination with urea and low temperature

Bonafe CFS, Vital CMR, Telles RCB, Gonçalves MC, Matsuura MSA, Pessine FBT, Freitas DRC, Vega J*

The effect of low temperature and urea combined with high pressure was studied on tobacco mosaic virus (TMV). The evaluation of its aggregation state and denaturation process was studied using gel filtration, transmission, electron microscopy, and spectroscopic methods. The incubation at 2.5 kbar induced 18% dissociation, and decreasing of temperature to -19 °C promoted additional dissociation to 72%, with stabilization of the dissociation products. Under such conditions , extensive denaturation did not occur. The apparent enthalpy and entropy of dissociation indicated that the TMV association is an entropicly driven process. The apparent free energy of stabilization given by the presence of RNA is at least -1.7 kcal/mol subunit. Urea-induced dissociation of TMV samples and incubation at high-pressure promoted a higher degree of dissociation. High-pressure induced remarkable TMV denaturation in the presence of 2.5 M urea, with a volume change of -101 mL/mol of denatured subunit. The apparent enthalpy and entropy of denaturation by 1.75 M urea at 2.5 kbar was -11.1 and -10.2 kcal/mol subunit, respectively, demonstrating that the TMV protein coat presents an apparent free energy of denaturation by urea close to zero. These thermodynamic parameters could be derived by assuming a steady-state condition. Biochemistry 37: 11097-11105, 1998

P004-98 Indole-3-acetic acid biosynthesis by bacteria Xanthomonas axonopodis cv citri is increased in the presence of leaf extracts

Costacurta A, Mazzafera P*, Rosato YB

Indole-3-acetic acid production by Xanthomonas strains pathogenic to citrus was analyzed by reversed-phase high-performance liquid chromatography, thin-layer chromatography, UV spectroscopy and gas chromatography-mass spectrometry, and quantified by high-performance liquid chromatography with fluorescence detection. Amounts of auxin produced by Xanthomonas strains were low when compared with indole-3-acetic acid biosynthesis by other bacteria. In three different experiments it was shown that the addition of plant leaf extracts to bacterial cultures increased indole-3-acetic acid biosynthesis by Xanthomonas axonopodis pv. citri 223. Microbiology Letters 159: 215-220, 1998

P005-98 Oil content of green beans from some coffee species

Mazzafera P*, Soave D, Zullo MAT, Guerreiro Filho O

The oil content was determinei in seeds of several continental African species of the coffee germplasm bank of Instituto Agronômico de Campinas, State of São Paulo, Brazil. Oil was extracted from seeds with hexane in Soxhlet apparatus. Due to the economic importance, C. arabica and C. canephora have been the best studied species concerning oil content and composition, and the results obtained are in agreement with the reported in the literature. On the other hand, only one report in the literature describes the results of oil analyses in other few species of the African continent, aithough it does not allow comparison with our results. The oil content of most of the species varied from 9 to 15%, therefore, similar to the range observed for C. arabica and C. canephora. The exception was C. salvatrix, with 29% of oil in the seeds. Bragantia 57: 45-48, 1998

P006-98 Growth and biochemical alterations in coffee due to selenite toxicity

Mazzafera P*

Two experiments were conducted to investigate selenite toxicity in coffee (Coffea arabica cv. Catuaí). In the first aqueous selenite solution (10 gM Na2SeO3) was used to infiltrate leaves of an adult coffee plant. The infiltrated leaves and fruits adjacent to them showed enhanced contents of caffeine and soluble sugars. Amino acid contents were not affected, whereas pigments (chlorophylls, carotenoids and xanthophylls) exhibited a significant decrease. In the second experiment, coffee seedlings were irrigated with aqueous selenite solutions (10,100 and 1000 JIM Na2SC03) and the first and third pairs of leaves were analyzed. Control plants did not receive selenium. The plants were not different in height, but at the highest selenium concentration showed lower dry matter accumulation in roots and leaves, lower leaf area and thicker leaves. Increases in caffeine and soluble sugars were observed in the first pair of leaves at the highest selenium concentration, although selenium content itself increased steadily with increasing solution concentration. Phenols increased in both leaf pairs and pigments decreased in the third pair. Nitrate reductase activity, measured in the second leaf pair, was much lower at all selenium levels. The profile of free amino acid was altered in leaves of plants treated with selenium.
Plant and Soil 201: 189-196, 1998

P071-98 Differential expression of a novel gene in response to coronatine, methyl jasmonate, and wounding in the coil mutant of Arabidopsis

Benedetti CE, Costa CL, Turcinelli SR, Arruda P*

Coronatine is a phototoxin produced by some plant-pathogenic bacteria. It has been shown that coronatine mimics the action of methyl jasmonate (MeJA) in plants. MeJA is a plant-signaling molecule involved in stress responses such as wounding and pathogen attack. In Arabidopsis thaliana, MeJA is essential for pollen grain development. The coil (for coronatine-insensitive) mutant of Arabidopsis produces sterile male flowers and shows an altered response to wounding. When the differential display technique was used, a message was rapidly induced by coronatine in wild-type plants but not in coil. The corresponding cDNA was cloned. The coronatine-induced gene ATHCOR1 (for A. thaliana coronatine-induced) is expressed in seedlings, mature leaves, flowers, and siliques but was not detected in roots. The expression of this gene was dramatically reduced in coil plants, indicating that COI1 affects its expression. ATHCORRR1 was rapidly induced by MeJA and wounding in in wild-type plants. The sequence of ATHCOR1 shows no strong homology to known proteins. However, the predicted polypeptide contains a conserved amino acid sequence present in several bacterial, animal and plant hydrolases and includes a potential ATP/GTP-binding-site motif (P-loop).
Plant Physiology 116: 1037-1042, 1998

P072-98 The molecular and functional characterization of an Opaque2 homologue gene from Coix and a new classification of plant bZIP proteins

Vettore AL, Yunes JA, Neto GC, da Silva MJ, Arruda P*, Leite A

The seed storage proteins of Coix, sorghum and maize are codified by homologous genes which are coordinately expressed in the endosperm in a temporal-specific fashion. Opaque2 (O2), a bZIP protein originally isolated from maize, has been described as a transcription activator of alpha- and beta-prolamin genes. The isolation and characterization of cDNA and genomic clones encoding the Opaque2 homologue from Coh are reported here. The coding region of the Coix O2 gene is interrupted by five introns and codifies a polypeptide of 408 amino acids. Comparison of the deduced amino acid sequence with two different sequences of maize O2 protein showed that the Coix O2 protein is similar to the maize O2 isolated from W22 maize inbred line. The Coix O2 protein has the same binding specificity and expression pattern of the maize O2. The O2 proteins together with OHP1, OsBZIPPA, SPA, CPRF2 and RITA1 were assigned to one of the five bZIP plant families in an updated classification of plant bZIP according to bZIP domain similarity. Plant Molecular Biology 36: 249-263, 1998

P073-98 Cooperative DNA binding and sequence discrimination by the Opaque2 bZIP factor

Yunes JA, Vettore AL, Silva MJ, Leite A, Arruda P*

The maize Opaque2 O2) protein is a basic leucine zipper transcription factor that controls the expression of distinct classes of endosperm genes through the recognition of different cis-acting elements in their promoters. The O2 target region in the promoter of the –coixin gene was analyzed in detail and shown to comprise two closely adjacent binding sites, named O2u and O2d, which are related in sequence to the GCN4 binding site. Quantitative Dnase footprint analysis indicated that O2 binding to –coixin target sites is best described by a cooperative model. Transient expression assays showed that the two adjacent sites act synergistically. This synergy is mediated in part by cooperative DNA binding. In tobacco protoplasts, O2 binding at the O2u site is more important for enhancer activity than is binding at the O2d site, suggesting that the architecture of the O2-DNA complex is important for interaction with the transcriptional machinery.
Plant Cell 10: 1941-1956, 1998


C001-98 N2 fixation in Crotalaria juncea L.: effect of NO3 and NH4

Mendonça E, Schiavinato M*

In Proceedings of 16th World Congress of Soil Science, 20 - 26/08/1998, Montpellier, FRANÇA, trabalho completo em CDROM



A062-98 = A067-98


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