Microsporogenesis analysis validates the use of artificially tetraploidized Brachiaria ruziziensis in breeding programs.

The genus Brachiaria contains species that have great economic importance in the Brazilian agricultural sector, as they enable cattle ranching on acid and poor soils with species that are resistant to spittlebugs and form crop-livestock-forest integration systems. The genus mainly consists of tetraploid (2n = 4x = 36) and apomictic species such as B. decumbens and B. brizantha. Sexuality is found in diploid species (2n = 2x = 18) such as B. ruziziensis. Interspecific hybridization between species of interest is possible by the artificial tetraploidization of B. ruziziensis and the subsequent hybridization with genotypes of B. brizantha and B. decumbens. Therefore, tetraploidized plants have to have normal meiosis or low rates of irregularities, as well as produce viable pollen grains. The objective of this study was to compare meiosis and pollen grain viability and morphology in artificially tetraploidized B. ruziziensis with that of descendants generated from crossing and selfing. The frequency of meiotic abnormalities ranged from 4.43 to 11%, and pollen viability ranged from 61 to 85%. Abnormalities were detected from prophase I to the tetrad stage with a variable frequency between the genotypes. The meiotic behavior of the artificially tetraploidized plants was little affected, and the pollen viability of the genotypes was high. Regarding pollen grain ultrastructure, there were no variations or morphological changes in the different genotypes. The genotypes have meiotic stability and high pollen viability, and can be incorporated into Brachiaria breeding programs.

Interleukin-2 and interleukin-4 increase the survival of retinal ganglion cells in culture.

Natural cell death is a degenerative phenomenon observed during the normal development of the nervous system. The neuroprotective effects of cytokines produced by neuronal, glial or infiltrating cells on neurons have been extensively studied. In this work we studied the role of interleukin (IL)-2 and IL-4 on the survival of retinal ganglion cells (RGC) after 48 h in culture. Our results demonstrate that the effect of both ILs was dose-dependent and the treatment with either IL-2 (50 U/ml) or IL-4 (5 U/ml) induced a 2-fold increase in RGC survival. The effect of IL-4, but not of IL-2, was totally abolished by either 20 microM 5-fluoro-2'-deoxyuridine, an inhibitor of cell proliferation, or by 1 microM telenzepine, an inhibitor of M1 muscarinic receptor. Our results suggest that both cytokines could play an important role during the development of retinal tissue as well as during retina trauma.