2012 January

Masked mRNAs are stored within nuclear speckles

The microspore of the water fern Marsilea vestita undergoes desiccation to become a stable storage structure that will later produce the male gametophyte of the plant. The spores become transcriptionally silent during desiccation, as newly transcribed pre-mRNAs are stored in nuclear speckles in association with known splicing components. The dynamic distribution of mRNA and nuclear speckles was investigated by using a modified FISH approach. During microspore desiccation, nuclear speckles containing masked RNA essential for spermatogenesis aggregate into a single, large coalescence. Upon rehydration of the dry spore, the male gametophyte undergoes rapid development and spermatogenesis is initiated. The speckle aggregate is displaced to the cytoplasm of the antheridial mother cell during the first division of the gametophyte. The speckles, containing their mRNAs, then fragment and become distributed among the forming spermatogenous cells of the developing gametophyte. Speckle dispersion is dependent on the Exon Junction Complex core component Mago nashi. Immunostaining of a microspore shows co-localization of the nuclear speckle marker U2B" (red) and Poly(A)+ RNA (green) in a single aggregate within the DAPI-stained nucleus (blue).

Taken from: Stephen M. Wolniak et al., 2011, BMC Cell Biology [View article]