Possible Critical Mass (kD) Value Limiting Expression of Drosophila melanogaster Pupae under Microgravity Conditions

This study aimed to identify microgravity-responsive regulatory genes in Drosophila melanogaster using our microarray dataset. Contrary to expectations, we found that known regulators did not respond to microgravity, prompting a reevaluation of how the 807 identified genes might be regulated. We hypothesized that the differential travel time of polymerase affects transcript production, suggesting that smaller RNA strands correlate with higher expression levels. This led us to calculate a critical mass (kD) of 36.6875 ± 1.36 kD, centered at 1000 bp of mRNA, marking a transition from positive to negative gene expression under microgravity conditions.

Of the 807 IDs initially identified, only 741 corresponded to unique genes, while some IDs lacked gene associations or corresponded to multiple genes. Notably, six IDs identified via correlation analysis included five genes (ImpL-3, DnaJ1, CG4726, CG14598, CG5326) that showed over 78% detection across 10,750 iterations. Validation of our correlation approach involved repeating a 2003 experiment, confirming a consistent negative expression profile in 2010. We also selected four positively regulating genes (CG5703, Surf1, CG8885, CG1970) and one negative regulator (Mef2) to explore their roles. Further investigation of 134 genes that anchor transcription factor binding sites revealed no response to microgravity. Analyzing mRNA lengths, we focused on the isoform region around 1000 bp, calculating mean values and standard deviations, reinforcing that the critical mass affecting expression in Drosophila pupae under microgravity is approximately 36.6875 kD.