Space radiation and microgravity are recognized as primary and inevitable risk factors for humans traveling in space, but the reports regarding their synergistic effects remain inconclusive and vary across studies due to differences in the environmental conditions and intrinsic biological sensitivity. Thus, we studied the synergistic effects on transcriptional changes in the global genome and DNA damage response (DDR) by using
dys-1 mutant and
ced-1 mutant of C. elegans, which respectively presented microgravity-insensitivity and radiosensitivity when exposure to spaceflight condition (SF) and space radiation (SR). The
dys-1 mutation induced similar transcriptional changes under both conditions, including the transcriptional distribution and function of altered genes. The majority of alterations were related to metabolic shift under both conditions, including transmembrane transport, lipid metabolic processes and proteolysis. Under SF and SR conditions, 12/14 and 10/13 altered pathways, respectively, were both grouped in the metabolism category. Out of the 778 genes involved in DDR, except
eya-1 and
ceh-34, 28 altered genes in
dys-1 mutant showed no predicted protein interactions, or anti-correlated miRNAs during spaceflight. The
ced-1 mutation induced similar changes under SF and SR; however, these effects were stronger than those of the
dys-1 mutant. The additional genes identified were related to phosphorous/phosphate metabolic processes and growth rather than, metabolism, especially for environmental information processing under SR. Although the DDR profiles were significantly changed under both conditions, the
ced-1 mutation favored DNA repair under SF and apoptosis under SR. Notably, 37 miRNAs were predicted to be involved in the DDR. Our study indicates that, the
dys-1 mutation reduced the transcriptional response to SF, and the
ced-1 mutation increased the response to SR, when compared with the wild type C. elegans. Although some effects were due to radiosensitivity, microgravity, depending on the dystrophin, exerts predominant effects on transcription in C. elegans during short-duration spaceflight.