Members of a small family of nodulin-like genes are regulated under iron deficiency in roots of Arabidopsis thaliana

The analysis of rapid responses in the transcriptome of Arabidopsis roots to a decreased iron (Fe) supply was studied using DNA microarrays and revealed candidate genes with putative roles in Fe homeostasis. In addition to the frequently reported induction of gene activity in response to Fe deficiency, the expression of a number of putative cationic metal transporters was found to rapidly decrease in response to Fe deficiency. In this report we have investigated a small family of five nodulin-like genes that show protein sequence similarity to AtVIT1 and likely have a function in regulation of Fe homeostasis. DNA microarray analysis showed a rapid decrease in transcript abundance for nodulin-like1 (At1g21140), nodulin-like2 (At1g76800), and nodulin-like21 (At3g25190). This decrease was significant after 6 h of Fe deficiency and persisted at least to 72 h. Nodulin-like3 (At3g43630) and Nodulin-like4 (At3g43660) did not respond to the Fe concentration in the microarray analysis. The nodulin-like family encoded presumptive membrane proteins with five calculated transmembrane domains, and all members had significant protein sequence homology to the vacuolar Fe transporters AtVIT1 and ScCCC1p. Homologs of all five nodulin-like genes were found in both di- and monocotyledon plants, as well as in Physcomitrella and Chlamydomonas. Promoter-beta-glucuronidase (GUS) assays showed expression of the nodulin-like1 gene in roots, hypocotyls, and expanded cotyledons of two-week-old Arabidopsis seedlings with the greatest activity associated with the vascular bundle and the root stele. In the absence of Fe, GUS activity was greatly reduced and was only weakly visible in the stele and vascular bundle. In an attempt to identify the function of these nodulin-like proteins, we isolated knockout mutants for nodulin-like3 and nodulin-like21 from available T-DNA insertion lines. Although these mutants did not show dramatic changes in growth or in their ability to grow on Fe-deficient media or media containing from 5 to 120 mu M Fe, the nodulin-like3 mutant had a significantly higher Fe concentration in the shoots and both nodulin-like3 and nodulin-like21 mutants had significantly decreased Fe in the roots. These results were taken as an indication, that some members of this nodulin-like family were directly involved in Fe homeostasis in plants. (C) 2011 Elsevier Masson SAS. All rights reserved

Variações do conteúdo de glucose, frutose e sorbitol em gemas e ramos de macieira durante a dormência Variations of glucose, frutose and sorbitol content in buds and stems of apple tree during the dormancy period

O objetivo deste trabalho foi determinar as variações do conteúdo de glucose, frutose e sorbitol em gemas e ramos de um ano de macieira durante o período de dormência. Os ramos da cultivar "Imperial Gala" foram coletados em Porto Amazonas-PR, em intervalos de 21 dias, de abril a agosto (19/04, 10/05, 31/05, 21/06, 12/07, 02/08 e 23/08), e receberam ou não tratamento com frio suplementar de 1.440 horas à temperatura de 4 a 7&deg;C. As análises dos carboidratos foram realizadas em gemas e porções de ramos adjacentes às primeiras por cromatografia líquida de alta eficiência (HPLC). Ocorreu um acúmulo de glucose, frutose e sorbitol nas gemas de macieira durante a dormência. O acúmulo de glucose e frutose nos ramos aconteceu até o início de agosto quando, em seguida, houve redução, enquanto o sorbitol decresceu até junho e, em seguida, elevou-se até o final de agosto. O tratamento com frio ao longo da dormência modificou as variações dos conteúdos de carboidratos nas gemas e ramos de macieira.<br>This research was aimed at evaluating the variations of glucose, frutose and sorbitol content in one year old buds and stems of apple trees during the dormancy period. The stems of cv. Imperial Gala were collected in Porto Amazonas, Parana State, Brazil, at intervals of 21 days from April to August (April 19th, May 10th, May 31st, June 21st, July 12th, August 2nd and August 23rd) and were treated or not with 1,440 hours of chill (4 to 7&deg;C). The carbohydrates were analysed in buds and stem tissues close to buds by high performance liquid chromatography (HPLC). There was an increase of glucose, frutose and sorbitol content in apple tree buds during the dormancy. An increase of glucose and frutose content in stems occured until August 2nd followed by a significative reduction, while the sorbitol content decreased until June 21st followed by an increase until August 31st. The chill treatment during the dormancy period modified the variations of carbohydrate contents in buds and stems of apple tree