BackgroundGluconacetobacter diazotrophicus Pal5 is an endophytic diazotrophic bacterium that lives in association with sugarcane plants. It has important biotechnological features such as nitrogen fixation, plant growth promotion, sugar metabolism pathways, secretion of organic acids, synthesis of auxin and the occurrence of bacteriocins.ResultsGluconacetobacter diazotrophicus Pal5 is the third diazotrophic endophytic bacterium to be completely sequenced. Its genome is composed of a 3.9 Mb chromosome and 2 plasmids of 16.6 and 38.8 kb, respectively. We annotated 3,938 coding sequences which reveal several characteristics related to the endophytic lifestyle such as nitrogen fixation, plant growth promotion, sugar metabolism, transport systems, synthesis of auxin and the occurrence of bacteriocins. Genomic analysis identified a core component of 894 genes shared with phylogenetically related bacteria. Gene clusters for gum-like polysaccharide biosynthesis, tad pilus, quorum sensing, for modulation of plant growth by indole acetic acid and mechanisms involved in tolerance to acidic conditions were identified and may be related to the sugarcane endophytic and plant-growth promoting traits of G. diazotrophicus. An accessory component of at least 851 genes distributed in genome islands was identified, and was most likely acquired by horizontal gene transfer. This portion of the genome has likely contributed to adaptation to the plant habitat.ConclusionThe genome data offer an important resource of information that can be used to manipulate plant/bacterium interactions with the aim of improving sugarcane crop production and other biotechnological applications.

Chayote (Sechium edule) (Cucurbitaceae), also known as vegetable pear, mirliton, or mango squash, is a commercially important vegetable crop in Brazil, where it is affected by chayote witches'-broom disease. Affected plants exhibit witches'-broom growths and other symptoms characteristic of plant diseases caused by phytoplasmas. Since previous electron microscopic studies revealed the association of a phytoplasma with chayote witches'-broom, the present work was aimed at detecting and classifying the phytoplasma that may be the causal agent of the disease. Strains of a phytoplasma belonging to group 16SrIII (X-disease phytoplasma group) were discovered in chayote affected by witches'-broom disease and in diseased plants of Momordica charantia that were growing as weeds in fields of chayote in Brazil. On the basis of results from restriction fragment length polymorphism and nucleotide sequence analyses of 16S rDNA, the phytoplasma was classified in a new subgroup, designated subgroup III-J. This classification was supported by a phylogenetic tree constructed by the Neighbor-Joining method.

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The biflavonoid 2'',3''-diidroochnaflavone ( 1), isolated from the leaves of Luxemburgia nobilis, was cytotoxic to murine Ehrlich carcinoma (IC50 = 17.2 microM) and human leukemia K562 cells (IC50 = 89.0 microM) in a concentration-dependent manner in 45 h cell culture. The acetyl (1a) and methyl (1b) derivatives of 1 were not cytotoxic to these tumour cells at 67.0 and 82.0 microM concentrations, respectively. Biflavonoid 1 as well 1a inhibit the activity of human DNA topoisomerases I and II-alpha as observed in relaxation and decatenation assays. In addition, we show that 1 is a DNA interacting agent, which causes DNA unwinding in an assay with topoisomerase I. Also, spectrophotometric titration of 1 with DNA resulted in a pronounced hypochromic effect.

RESUMOPalavras-chave adicionais: Vigna unguiculata, Comovirus, Potyvirus, melhoramento genético.Among the viruses tha t infect cowpea ( Vign a u n gu ic u lata L . Walp.), Cowpea severe mosaic virus (CPSMV) and Cowpea aphidb o rn e mo saic v iru s (CABMV) a re highlighted for their severity a n d wid esp rea d o ccu rr enc e, respe cti vel y. T h ere for e, the a im of t h is st u d y wa s t o o b t a i n a nd e v a l u a t e c o wpe a pl a n t s sh o wi n g resist a nce to CPS MV a nd CABMV in order t o develop n ew a nd e sse n t i a ll y d er i v e d c u l t iv a r s. E i g ht c r o sse s we r e pe r fo r me d , fo llo wed by ba c k cro sse s, u si ng t he lin e T E 9 7 -3 0 9 G-9 a n d t he cu l tiva r Pa ta tiva a s re sista nt pa rent a l do nors, a nd the c u ltiv a rs BR3-Tracuateua, BRS-Urubuquara, BRS-Novaera, BRS-Guariba and Pretinho a s su sceptible pa rents. Generations F2 a nd F2 RC1 were challenged for resista nce by mechanically inocu lating CPSMV a nd CABMV isolates. In F2RC1 genera tions, besides resista nce, other Barros, G.B.; Nogueira, M.S.R.; Oliveira, C.R.R.; Freire Filho, F.R.;Ribeiro, V.Q.; Veiga, C.F.M.; Brioso, P.S.T.; Eiras, M. Obtaining cowpea plants resistant to Cowpea severe mosaic virus and Cowpea aphid-borne mosaic virus. Summa Phytopathologica, v.39, n.2, p.130-136, 2013. traits were evaluated: number of days to the beginning of flowering, pod length, nu mber of seeds.pod-1, weight of 100 seeds, and yield of seeds.plant-1. All F2 and F2RC1 individuals were analyzed by the  2 test a nd fit to the expected frequency of 15 susceptible plants: 1 plant resistant to both viruses. The means of resistant F2RC1 plants, from each backcross, were compared with the mean of their respective recurrent parent by the t-test and means of backcrosses were compared by the Scott-Knott test. Genetic va riability among back crosses was detected for all traits. All backcrosses were considered promising for obta ining essentia lly derived cu ltiva rs resista nt to CPSMV a nd CABMV, and the selected plants have characteristics that allow the selection of lines with highly productive grains of good commercial quality.Dentre os vírus que infectam o feijão-caupi (Vigna ung uiculata L. Wa lp.) desta ca m-se, respectiva mente, pela severidade e ampla ocorrência o Cowpea severe mosaic virus (CPSMV) e o Cowpea aphidborne mosaic virus (CABMV). Portanto, objetivaram-se, no presente tra balho, obter e ava liar plantas de feijão-cau pi com resistência ao CPSMV e ao CABMV, visa ndo a o desenvolvimento de cu ltivares essencia lmente deriva da s e novas cu ltiva res. Rea liza ra m-se oito cruzamentos seguidos de retrocruzamentos, utilizando a linhagem TE 9 7 -30 9 G-9 e a cu ltiva r Pa ta tiva como genitores resistentes, e a s cu ltivares BR3 -Tra cua teu a, BRS-Urubu qua ra, BRS-Novaera, BRSGuariba e Pretinho como genitores suscetíveis. As gerações F 2 e F 2 RC 1 foram desafiadas quanto à resistência por meio de inoculação mecânica com isolados do CPSMV e do CABMV. Nas gerações F 2 RC 1 , além da resistência for...