| Summary: | 博士 === 國立臺灣大學 === 微生物與生化學研究所生物化學組 === 92 === In mammals, TUBBY-like proteins play an important role in the maintenance and function of neuronal cells during post-differentiation and development. We have identified a TUBBY-like protein gene family with eleven members in Arabidopsis, named AtTLP1-11. Although seven of the AtTLP genes are located on chromosome I, no local tandem repeats or gene clusters are identified. Except for AtTLP4, RT-PCR analysis indicates that all these genes are expressed in various organs in 6-week-old Arabidopsis. AtTLP 1, 2, 3, 6, 7, 9, 10 and 11 are expressed ubiquitously in all the organs tested but the expression of AtTLP5 and 8 shows dramatic organ-specificity. These eleven family members share 30 — 80% amino acid similarities across their conserved C-terminal tubby domains. Unlike the highly diverse N-terminal region of animal TUBBY-like proteins, all AtTLP members except AtTLP8 contain a conserved F-box domain (51-57 residues). The interaction between AtTLP9 and ASK1 (Arabidopsis Skp1-like 1) is confirmed via yeast two-hybrid assays. ABA-insensitive phenotypes are observed for two independent AtTLP9 mutant lines, whereas transgenic plants overexpressing AtTLP9 are hypersensitive to ABA during seed germination and early seedling development. These results suggest that AtTLP9 may participate in the ABA signaling pathway. Real-time PCR experiments were used to quantify AtTLP9 transcript levels. We have shown that AtTLP9 expression is transiently up-regulated after imbibition of seeds. The results of subcellular localization have shown that AtTLP9 is present both in nuclei and out of nuclei.
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