Different responses of invasive and native species to elevated CO2 concentration

Increasing atmospheric CO₂ concentration is regarded as an important factor facilitating invasion. However, the mechanisms by which invasive plants spread at the expense of existing native plants are poorly understood. In this study, three invasive species (Mikania micrantha, Wedelia trilobata and Ipomoea cairica) and their indigenous co-occurring species or congeners (Paederia scandens, Wedelia chinensis and Ipomoea pescaprae) in South China were exposed to elevated CO₂ concentration (700 μmol mol^?1). The invasive species showed an average increase of 67.1% in photosynthetic rate, significantly different from the native species (24.8%). On average the increase of total biomass at elevated CO₂ was greater for invasive species (70.3%) than for the natives (30.5%). Elevated CO₂ also resulted in significant changes in biomass allocation and morphology of invasive M. micrantha and W. trilobata. These results indicate a substantial variation in response to elevated CO₂ between these invasive and native plant species, which might be a potential mechanism partially explaining the success of invasion with ongoing increase in atmospheric CO₂.     

Comparison of locomotor behaviour between white-headed langurs Trachypithecus leucocephalus and Franois' langurs T. franoisi in Fusui,China

We studied the locomotor behaviour of white-headed langurs Trachypithecus leucocephalus and Franois' langurs T.franoisi to test two hypotheses:(1) these monkeys have evolved locomotor ability to support their activities on limestone hills,and (2) Franois' langurs have evolved more diverse locomotor skills than white-headed langurs. Data were collected from 1996-1998 and in 2005 in Fusui Nature Reserve,Guangxi,and showed that the two species had similar locomotor types,but Franois' langurs had more locom...     

Structure of the catalytic domain of human DOT1L,a non-SET domain nucleosomal histone methyltransferase

Dot1 is an evolutionarily conserved histone methyltransferase that methylates lysine-79 of histone H3 in the core domain. Unlike other histone methyltransferases, Dot1 does not contain a SET domain, and it specifically methylates nucleosomal histone H3. We have solved a 2.5 A resolution structure of the catalytic domain of human Dot1, hDOT1L, in complex with S-adenosyl-L-methionine (SAM). The structure reveals a unique organization of a mainly alpha-helical N-terminal domain and a central open alpha/beta structure, an active site consisting of a SAM binding pocket, and a potential lysine binding channel. We also show that a flexible, positively charged region at the C terminus of the catalytic domain is critical for nucleosome binding and enzymatic activity. These structural and biochemical analyses, combined with molecular modeling, provide mechanistic insights into the catalytic mechanism and nucleosomal specificity of Dot1 proteins.     

Gibberellin regulates Arabidopsis floral development via suppression of DELLA protein function

The phytohormone gibberellin (GA) regulates the development and fertility of Arabidopsis flowers. The mature flowers of GA-deficient mutant plants typically exhibit reduced elongation growth of petals and stamens. In addition, GA-deficiency blocks anther development, resulting in male sterility. Previous analyses have shown that GA promotes the elongation of plant organs by opposing the function of the DELLA proteins, a family of nuclear growth repressors. However, it was not clear that the DELLA proteins are involved in the GA-regulation of stamen and anther development. We show that GA regulates cell elongation rather than cell division during Arabidopsis stamen filament elongation. In addition, GA regulates the cellular developmental pathway of anthers leading from microspore to mature pollen grain. Genetic analysis shows that the Arabidopsis DELLA proteins RGA and RGL2 jointly repress petal, stamen and anther development in GA-deficient plants, and that this function is enhanced by RGL1 activity. GA thus promotes Arabidopsis petal, stamen and anther development by opposing the function of the DELLA proteins RGA, RGL1 and RGL2.     

Proteomic analysis of soybean root hairs after infection by Bradyrhizobium japonicum

Infection of soybean root hairs by Bradyrhizobium japonicum is the first of several complex events leading to nodulation. In the current proteomic study, soybean root hairs after inoculation with B. japonicum were separated from roots. Total proteins were analyzed by two-dimensional (2-D) polyacrylamide gel electrophoresis. In one experiment, 96 protein spots were analyzed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) to compare protein profiles between uninoculated roots and root hairs. Another 37 spots, derived from inoculated root hairs over different timepoints, were also analyzed by tandem MS (MS/MS). As expected, some proteins were differentially expressed in root hairs compared with roots (e.g., a chitinase and phosphoenolpyruvate carboxylase). Out of 37 spots analyzed by MS/MS, 27 candidate proteins were identified by database comparisons. These included several proteins known to respond to rhizobial inoculation (e.g., peroxidase and phenylalanine-ammonia lyase). However, novel proteins were also identified (e.g., phospholipase D and phosphoglucomutase). This research establishes an excellent system for the study of root-hair infection by rhizobia and, in a more general sense, the functional genomics of a single, plant cell type. The results obtained also indicate that proteomic studies with soybean, lacking a complete genome sequence, are practical.