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A role for Taiman in insect metamorphosis
Jesus Lozano1, Takumi Kayukawa2, Tetsuro Shinoda2
1Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain.
Plos Genetics
|October 31, 2014
Summary
The Taiman (Tai) protein complex is crucial for juvenile hormone (JH) signaling. Specific Tai isoforms containing insertion 1 (IN-1) repress metamorphosis in insects, as shown in Blattella germanica.
Area of Science:
- Molecular Endocrinology
- Developmental Biology
- Insect Physiology
Background:
- The Methoprene-tolerant (Met) and Taiman (Tai) complex is identified as the juvenile hormone (JH) receptor in vitro.
- In vivo studies confirm Met's role in JH signaling, but Tai's function is unclear due to lethal depletion effects in some species.
- Tai isoforms, arising from sequence variations like indels, may be widespread in insects.
Purpose of the Study:
- To investigate the in vivo function of Taiman (Tai) isoforms in juvenile hormone (JH) signal transduction.
- To determine the role of specific Tai isoforms, particularly those with insertion 1 (IN-1), in insect metamorphosis.
- To elucidate the molecular mechanisms by which Tai influences JH-mediated developmental processes.
Main Methods:
- Identification and characterization of four Tai isoforms in the cockroach Blattella germanica, resulting from C-terminal indels.
- RNA interference (RNAi) to deplete specific Tai isoforms in B. germanica and assess effects on survival and development.
- Reporter assays using a JH response element (kJHRE) in conjunction with Met and Tai isoforms from B. germanica and Tribolium castaneum.
Main Results:
- Concomitant depletion of all four Tai isoforms in B. germanica caused 100% mortality.
- Depletion of only insertion 1 (IN-1) containing Tai isoforms in B. germanica significantly reduced mortality and induced precocious adult development in about half of the specimens.
- Both T. castaneum Tai isoforms (IN-1 containing and DEL-1 lacking) activated a JH response element (kJHRE) with Met and JH in reporter assays.
Conclusions:
- Tai isoforms containing IN-1 are essential for transducing the JH signal that represses metamorphosis in insects.
- Tai plays a critical role in the molecular mechanisms governing JH-mediated metamorphosis, at least in B. germanica.
- Distinguishing between Tai isoforms is crucial for understanding its diverse functions in insect development and other biological processes.
