Characterization of a pollen-specific cDNA from sunflower encoding a zinc finger protein.

The maize transposable element Activator (Ac) carries subterminal CpG-rich sequences which are essential for the transposition of the element. It has previously been shown that the methylation of certain sequences contained in this region can alter their ability to interact with the Ac-encoded protein. The novel hypothesis that the methylation of subterminal Ac sequences is required for transposition was tested. Approximately 150 bp of the 5' subterminal region of the Ac element was examined for the presence of 5-methylcytosines by the ligation-mediated polymerase chain reaction (LMPCR)-aided genomic sequencing method. The methylation status of 22 and 39 cytosines on either strand of the DNA were analysed in each of five different transgenic tobacco cultures carrying transposable Ac sequences. Ten micrograms of tobacco DNA were used for each base-specific cleavage reaction before amplification by LMPCR. All but one of the cytosines were unmethylated. Only a minor fraction of the Ac molecules was methylated at one cytosine residue. It is concluded that DNA methylation at the tested Ac sequences is not required for the transposability of Ac or Ds elements in tobacco cells.     

Detecting senescence: a new method for an old pigment

Cellular senescence is a state of irreversible cell cycle arrest induced by different types of cellular stresses. The field of senescence has made significant advances in the understanding of many of the mechanisms governing this phenomenon; however, a universal biomarker that unambiguously distinguishes senescent from proliferating cells has not been found. In this issue of Aging Cell, Evangelou and colleagues developed a sensitive method for identification of senescent cells in different types of biological material based on the detection of lipofuscin using an analogue of Sudan Black B (SBB) histochemical dye coupled with biotin, which they named GL13. The authors propose that this method is more sensitive and versatile than using SBB alone. Lipofuscin, a nondegradable oxidation product of lipids, proteins and metals, is found in senescent cells. Detection of lipofuscin using GL13 staining may be a more feasible method than others currently used for identification of senescent cells both in cell culture and tissues.     

The pollen of Caesalpinia pyramidalis Tul. is toxic to honeybees (Apis mellifera)

Caesalpinia pyramidalis Tul. (syn. Caesalpinia gardneriana Benth.) is an endemic tree from northeastern Brazil whose flowers are visited by a number of bee species, including the honeybee (Apis mellifera). The present study aimed to determine whether the pollen of C. pyramidalis is toxic to honeybees. Pollen samples were collected, dried, and added to food at doses of 0 (control), 2.5, 5.0, and 10 %. Each dose of food was fed to 60 honeybees, which were observed daily until the last one died. Statistical comparison of the survival curves was performed using the log-rank test. The mean survival times of the bees fed with C. pyramidalis pollen were 6.40 ± 0.28 days for the 2.5 % group, 5.70 ± 0.18 days for the 5.0 % group, 5.72 ± 0.23 days for the 10.0 % group, and 13.7 ± 0.61 days for the control group. All the pollen concentrations of C. pyramidalis significantly (P < 0.0001) reduced the survival of honeybees in comparison with control group. In conclusion, the results of our study show that the pollen produced by C. pyramidalis is toxic to A. mellifera under laboratory conditions.     

Sources and concentrations of silicon modulate the physiological and anatomical responses of Aechmea blanchetiana (Bromeliaceae) during in vitro culture

Plant Cell, Tissue and Organ Culture (PCTOC) - The use of silicon (Si) has been shown to be a good alternative to improve the growth and content of photosynthetic pigments of plants propagated in...