Methuselah‐likegenes affect development, stress resistance, lifespan and reproduction inTribolium castaneum

Abstract

Methuselah (Mth) is associated with lifespan, stress resistance and reproduction in Drosophila melanogaster, but Mth is not present in nondrosophiline insects. A number of methuselah-likes (mthls) have been identified in nondrosophiline insects, but it is unknown whether the functions of mth are shared by mthls or are divergent from them. Five mthls have been identified in Tribolium castaneum. Although they have different developmental expression patterns, they all enhance resistance to starvation. Only mthl1 and mthl2 enhance resistance to high temperature, whereas mthl4 and mthl5 negatively regulate oxidative stress in T. castaneum. Unlike in the fly with mth mutation, knockdown of mthls, except mthl3, shortens the lifespan of T. castaneum. Moreover, mthl1 and mthl2 are critical for Tribolium development. mthl1 plays important roles in larval and pupal development and adult eclosion, while mthl2 is required for eclosion. Moreover, mthl1 and mthl2 silencing reduces the fertility of T. castaneum, and mthl1 and mthl4 are also essential for embryo development. In conclusion, mthls have a significant effect on insect development, lifespan, stress resistance and reproduction. These results provide experimental evidence for functional divergence among mthls/mth and clues for the signal transduction of Mthls.

Identification, Characterization and Expression of Methuselah-Like Genes in Dastarcus helophoroides (Coleoptera: Bothrideridae)

“…Previous studies have demonstrated that D. melanogaster Mth-likes (homologous receptors of Mth) show high similarity to Mth and contain similar seven transmembrane (7tm) domains [3,37]. In our study, these three putative Mth-likes consisted of seven conserved transmembrane domains, which is consistent with the finding of a recent study in T. castaneum [38], although they only shared a moderate degree of sequence identity (24%, 29%, and 25% for Mth-like1, Mth-like2, and Mth-like5, respectively) with the Mth (NP-523871.1) of D. melanogaster .…”

“…Previous studies in D. melanogaster have shown that mth was expressed in both embryos and third-instar central nervous system (CNS) or discs, mth-like1 and mth-like5 were expressed in the embryo, while mth-like2 was not detected in whole embryos or third-instar brain and imaginal discs using in situ hybridization techniques [3]. A recent study suggested that the mRNA levels of mth-like1 of T. castaneum were highly expressed at the late egg, pupa, and early adult stage, and mth-like2 and mth-like5 were highly expressed at the early embryonic and late pupal stages [38]. Similarly to T. castaneum mth-like genes, mth-like genes of D. helophoroides were expressed throughout all of the larval, pupal, and adult stages, but to some extent they display different expression patterns, indicating that mth-like genes ( mth-like2 and mth-like5 ) of D. helophoroides were likely to have similar functions involved in larval and pupal development and the process of eclosion to T. castaneum mth-like genes, while functional divergence most likely occurred between T. castaneum and D. helophoroides mth-like genes ( mth-like1 ).…”

“…In the same recent study, when the expression of mth-like genes ( mth-like1 and mth-like2 ) was inhibited, one pair of beetles laid less eggs per day, but mth-like5 was not involved in fertility [38]. Previous studies have shown that the fertility of mth -mutated flies is decreased between 25 °C and 29 °C [11].…”

“…Conversely, the T. castaneum groups with suppression of mth-like1 , mth-like2 , and mth-like5 had a significantly shorter lifespan, which applied to both sexes [38], indicating that both mth and mth-like genes are involved in insect aging and are functionally divergent. However, both mth mutation in D. melanogaster and mth-like gene suppression in T. castaneum have been reported to result in lethality for pre-adults [1,38], which demonstrates that at least some activity of the mth and mth-like genes are essential for survival. In our study, the expression levels of both mth-like1 and mth-like5 increased significantly in the older groups (aged 20, 26, and 30 months), while mth-like2 firstly decreased, and then increased, finally recovering to the normal level (Figure 5).…”

“…A previous study on mth-like genes of T. castaneum showed that suppression of mth-like genes decreased resistance to the stress of oxidation ( mth-like5 ), high temperature ( mth-like1 and mth-like2 ), and starvation ( mth-like1 , mth-like2 , mth-like3 , mth-like4 , and mth-like5 ) [38]. In our study, the mRNA levels of mth-like1 , mth-like2 , and mth-like5 were all responsive to the stress of paraquat (Figure 6), only mth-like2 was responsive to the stress of high temperature (Figure 7), and mth-like2 and mth-like5 were responsive to starvation stress (Figure 8).…”