The data suggest that the REM34, REM35 and REM36 group is the most interesting one, as REM34 is co-expressed with the floral meristem identity (FMI) genes, they are bound by AP1, SVP, AP3 and PI, and they are expressed in the floral meristem and during the earliest stages of flower development. However, it appears that high levels of functional redundancy may conceal the exact function of these transcription factor genes.

No abstract

Over the last decades, most information on the mechanisms underlying tolerance to drought has been gained by considering this stress as a single event that happens just once in the life of a plant, in contrast to what occurs under natural conditions where recurrent drought episodes are the rule. Here we explored mechanisms of drought tolerance in coffee (Coffea canephora) plants from a broader perspective, integrating key aspects of plant physiology and biochemistry. We show that plants exposed to multiple drought events displayed higher photosynthetic rates, which were largely accounted for by biochemical rather than diffusive or hydraulic factors, than those submitted to drought for the first time. Indeed, these plants displayed higher activities of RuBisCO and other enzymes associated with carbon and antioxidant metabolism. Acclimation to multiple drought events involved the expression of trainable genes related to drought tolerance and was also associated with a deep metabolite reprogramming with concordant alterations in central metabolic processes such as respiration and photorespiration. Our results demonstrate that plants exposed to multiple drought cycles can develop a differential acclimation that potentiates their defence mechanisms, allowing them to be kept in an 'alert state' to successfully cope with further drought events.

No abstract

No abstract

RESUMO -(Nodulação, colonização micorrízica arbuscular e crescimento de algumas leguminosas nativas do Brasil). Foram examinados os efeitos da inoculação com rizóbio e micorriza, da fertilização com nitrogênio e fósforo na nodulação, na colonização micorrízica e no crescimento inicial das leguminosas arbóreas brasileiras Enterolobium contortisiliquum (Vell. Conc.) Morong, Inga laurina (Sw.) Willd., Lonchocarpus muehlbergianus Hassl e Platypodium elegans Vogel. O experimento foi conduzido em casa de vegetação usando sacos plásticos contendo uma mistura de solo arenoso de mata ciliar e vermiculita (2:1) fertilizados com nutriente basais incluindo NP, P e N inoculados ou não com rizóbio (r), micorriza (m) ou ambos (rm), totalizando sete tratamentos: NP, P, P+r, P+rm, N, N+m e N+rm, com dez repetições cada. As plantas foram analisadas aos 120 e 255 dias após o plantio. Tratamentos com deficiência de P afetaram negativamente o crescimento e nodulação de todas as espécies. Fungos micorrízicos arbusculares (FMAs) autóctones colonizaram as raízes do hospedeiro e as inoculações com fungos não aumentaram a colonização micorrízica, a qual foi favorecida pelo nível de P adicionado. A nodulação foi relativamente alta em E. contortisiliquum e L. muehlbergianus, principalmente em tratamentos contendo P, inoculados com rizóbio (P+r). Plantas deste tratamento desenvolveram-se melhor que as outras e, apesar dos rizóbios inoculados não apresentarem relações sinergísticas com os FMAs inoculados, também apresentaram as melhores porcentagens de colonização micorrízica. Além disso, estas duas espécies apresentaram maiores taxas de redução de acetileno e maior conteúdo de leghemoglobina. Estes resultados sugerem que E. contortisiliquum e L. muehlbergianus podem ter vantagens para se estabelecer em solos com baixos níveis de nitrogênio. Palavras-chave: rizóbio, dupla inoculação, Enterolobium contortisiliquum, Inga laurina, Lonchocarpus muehlbergianus, Platypodium elegansABSTRACT -(Nodulation, arbuscular mycorrhizal colonization and growth of some legumes native from Brazil). The effects of rhizobial and mycorrhizal inoculation, nitrogen and phosphorus fertilization on nodulation, mycorrhizal colonization and initial growth were examined in Brazilian native plants, Enterolobium contortisiliquum (Vell. Conc.) Morong, Inga laurina (Sw.) Willd., Lonchocarpus muehlbergianus Hassl and Platypodium elegans Vogel. The experiment was carried out in a glasshouse using plastic bags filled with a mixture of sandy soil from riparian forest and vermiculite (2:1) amended with basal nutrients including NP, P and N and infected with rhizobia (r), mycorrhiza (m) or both (rm), amounting seven treatments: NP, P, P+r, P+rm, N, N+m and N+rm, with ten replications each. The plants were analyzed at 120 and 255 days after sowing. P deficiency negatively affected growth and nodulation of all species. Autochton arbuscular mycorrhizal fungi (AMF) colonized host roots and fungal inoculations did not enhance mycorrhizal colonization, which was also favored by added P...

The Fungal Ribosomallntergenic Spacer Analysis (F-RlSA) was used to characterize soil fungal communities from three ecosystems of Araucaria angustifolia from Brazil: a native forest and two replanted forest ecosystems, one of them with a past history of wildfire. The arbuscular mycorrhizal fungi (AMF) infection was evaluated in Araucaria roots of 18-monthold axenic plants previously inoculated with soils collected from those areas in a greenhouse experiment. The principal componentanalysis ofF-RlSA profiles showed different soil fungal community betweenthe three studied areas. Sixty three percent ofF-RlSA fragments amplified in the soil and the substrate samples presented lengths between 500 and 700 bp. The number of Operational Taxonomic Units (OTUs) was 34 for soil and 38 for substrate, however, more fragments were detected in soil (214) than in substrate (163). An in silico F-RISA analysis to compare our data with ITSI-5.8S-ITS2 sequences from NCBI database showed the presence of Ascomycota, Basidiomycota and Glomeromycota among the soil and substrate fungal communities. AMF infection was higher in plants inoculated with soil from the native forest and the replanted forest with wildfire, both presenting similar chemical characteristics but with different disturbance levels. These results indicate that soil chemical composition may influence the soil fungal community structures rather than the anthropogenicor fire disturbances.

Dark septate endophytes (DSEs) constitute a polyphyletic group within the Ascomycota, with global distribution and a wide range of host plant species. The present study evaluated the diversity of DSE in sugarcane roots of the varieties RB867515, RB966928, and RB92579, and four varieties of not commercialized energy cane. A total of 16 DSE strains were isolated, mostly from the varieties RB966928 and RB867515, with six and five isolates, respectively. Just one of the four energy cane varieties had fungi with DSE appearance. The analyses of the DNA sequences from the internal transcribed spacer (ITS) and the large subunit (LSU), in association with the micromorphology of the isolates, allowed the differentiation of the 16 isolates in at least five species, within the families Periconiaceae, Pleosporaceae, Lentitheciaceae, Vibrisseaceae, and Apiosporaceae and the orders Pleosporales, Helotiales, and Xylariales. The order Pleosporales represented 80% of the isolates, and the species Periconia macrospinosa, with six isolates, accounted for the highest isolation frequency. The results confirm the natural occurrence of the DSE symbiosis in sugarcane varieties and the generalist character of these fungi as some of the detected species have already been reported associated with other host plants, ecosystems, and regions of the world.