| Summary: | 碩士 === 國立臺灣大學 === 農藝學研究所 === 106 === Root is an important organ, which provides several functions for plant growth including resource uptake from soil, anchorage, nutrient transport, and energy storage. Phytohormones are known to play vital roles in these processes. Our previous study has indicated that exogenously added ABA can induce root tip swelling in indica rice (TCN1). Since auxin can regulate many aspects of root development, including lateral root primordium formation and root hair elongation, in this study we investigated whether auxin plays a role in the ABA-mediated root tip swelling in rice. The results showed that ABA-mediated root tip swelling exists in both japonica and indica rice. Histochemical staining of GUS activity driven by an auxin-responsive synthetic promoter (DR5) shown that ABA-mediated root tip swelling was accompanied with a redistribution of auxin. The indole acetic acid (IAA) level was also increased in root tip region. Moreover, the effects of ABA on root tip swelling was repressed by Kynurenine (Kyn) or Yucasin, two auxin biosynthetic inhibitors and NPA, an auxin transporter inhibitor. However, the effects of inhibitors on ABA-mediated root tip swelling can be rescued by exogenous IAA. Meanwhile, auxin related and cell wall related genes were upregulated in root tip with ABA treatment. Taken together, these data suggest that ABA-mediated root tip swelling is dependent on the change of auxin biosynthesis and distribution.
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