Developmental growth is an intricate process involving the coordinated regulation of the expression of various genes, and microRNAs (miRNAs) play crucial roles in diverse processes throughout animal development. The ecdysone‐responsive miRNA, miR‐252, is normally upregulated during the pupal and adult stages of Drosophila development. Here, we found that overexpression of miR‐252 in the larval fat body decreased total tissue mass through a reduction in both cell size and cell number, causing a concomitant decrease in larval size. Furthermore, miR‐252 overexpression led to a delayed larval‐to‐pupal transition with defective anterior spiracle eversion, as well as a decrease in adult size and mass. Conversely, adult flies lacking miR‐252 showed an increase in mass compared with control flies. We found that miR‐252 directly targeted mbt, encoding a p21‐activated kinase, to repress its expression. Notably, co‐overexpression of mbt rescued the developmental and growth defects associated with miR‐252 overexpression, indicating that mbt is a biologically relevant target of miR‐252. Overall, our data support a role for the ecdysone/miR‐252/mbt regulatory axis in growth control during Drosophila development.
Two genes (TaLTP1 and TaLTP2) encoding lipid transfer proteins (LTPs) were isolated from a cDNA library constructed from leaf tissue harvested from 4-week-old seedlings of a wheat-rye near-isogenic line (NIL) involving a translocation of rye chromosome 2RL with wheat 2BS. The spatial and temporal patterns of expression of TaLTP1 and TaLTP2 were examined by Northern blot analysis and in situ hybridization. Both TaLTP1 and TaLTP2 contained a 270-bp open reading frame and encoded a putative LTP precursor molecule of 90 amino acids. Expression of the two LTPs was detected in leaves, stems, and crowns of the NILs but not in the roots. The expression levels of TaLTP1 and TaLTP2 remained constant in response to cold and ABA treatments over a period of 24 h but increased 3 days after the initiation of drought stress. An in situ hybridization study indicated that TaLTP1 was expressed in the cells within the vascular bundles of leaves and in the tissue layers between the vascular bundles in the crowns of the control and drought-treated plants. Expression of TaLTP1 in the tissue layers between the vascular bundles was higher in the drought-treated plants than in the control plants. The results suggested that high levels of expression of TaLTPs in the tissue layers between the vascular bundles might play a role in the drought tolerance response of the wheat crown.
Two-dimensional analysis of head extracts from Drosophila melanogaster identified the four eye-specific protein spots corresponding to the retinin protein. The retinin protein spots were specifically stained with phosphoprotein-specific dye, suggesting that the retinin protein undergoes post-translational modification by phosphorylation. Northern blot analysis showed that the retinin gene begins to be expressed during the late stage of puparium formation during development. Analysis of the N-terminal sequence and expression of the retinin gene in S2 suggest that retinin is a secretory protein. Transgenic flies with knockdown expression of the retinin gene by RNA interference (RNAi) were established. However, no significant phenotypic changes in eye structure or phototransduction were observed in the transgenic flies. Western blot analysis and immunohistochemical studies of D. melanogaster eyes suggest that retinin is a cornea-specific protein.
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