Poster: Tropisms

Abs # 665: Isolation and characterization of arabiposis mutants deficient in hydrotropism

Presenter:	Naoki, Negishi , 55020026@nodai.ac.jp
Authors	Naoki, Negishi  (A)   Gen, Takata  (A)   Koji, Koizumi  (A)   Yoichi, Sakata  (A)   Shigeo, Tanaka  (A)
Affiliations:	(A): Department of Bioscience, Tokyo University of Agriculture

Plant roots orient themselves to soil, responding appropriately to various stimuli such as water, gravity and touch. To elucidate the molecular mechanism of hydrotropism in roots of Arabidopsis thaliana, we developed a simple bioassay system based on hydrotropism and applied it to screening for mutants deficient in hydrotropism. Using our bioassay system, we have obtained 7 mutants from 4860 T-DNA tagged lines. To confirm that our mutants fail to respond specifically to water stimulus, we examined the gravitropic response and waving growth of the roots, the latter of which is caused by the stimuli of touch and gravity. All of the mutants showed a normal response to gravity as compared to the wild type. However, the mutant roots were wavier than the roots of wild type. Our mutants were also found to be sensitive to abscisic acid (ABA) when it was given externally, whereas ABA-insensitive mutant (abi2) was reported to be deficient in hydrotropism. On the other hand, 6 gravitropic mutants ( aux1,eir1,axr1,axr2,axr4,pgm1) given generously from ABRC responded normally to water stimulus. These results mentioned above suggested that the overall response of roots to water stimulus may differ essentially from gravitropic response in the perception, signal transduction and bending, although interaction was observed between hydrotropism and@gravitropism. It is also suggested that not only stimuli of touch and gravity but also water stimulus may be involved in the waving growth of roots in arabidopsis. Now we are analyzing the disrupted genes and their linkage to phenotype. The further studies will be discussed in the meeting.