Poster: Root Biology
Abs #
521: The defect in lateral root formation and root gravity response is associated with reduced auxin uptake in rice (Oryza sativa L.)
|
|
Presenter: |
Tsurumi, Seiji , tsurumis@scitec.kobe-u.ac.jp |
Authors | Tsurumi, Seiji (A) Chhun, Tory (B) Taketa, Shin (B) Ichii, Masahiko (B) | | Affiliations: |
(A): Radioisotope Research Center, Kobe University
(B): Faculty of Agriculture, Kagawa University
|
|
|
Auxins control growth and development in plants including lateral root formation and root gravity response, and application of exogenous auxin has been reported to promote lateral root formation. However, how endogenous auxin regulates these processes is largely unknown. In this report, the effects of auxins on lateral root formation and the mechanism for auxin sensitivity in rice were investigated using a lateral rootless mutant Lrt1 (Oryza sativa L. ssp. japonica cv. Oochikara). The Lrt1 was initially isolated in a screen for 2,4-dichlorophenoxyacetic acid (2,4-D) resistance and then characterized as a lateral rootless mutant controlled by a dominant gene.
In the present study, we found that exogenous application of indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA) rescued lateral root formation in Lrt1 seedlings whereas application of indole-3-acetic acid (IAA), a major endogenous auxin, did not induce lateral roots, suggesting that IBA but not IAA, plays very important role in lateral root formation in rice.
In addition to 2,4-D, Lrt1 seedlings also exhibited resistance to a synthetic auxin NAA, and natural auxins IAA and IBA. To clarify the molecular mechanism of auxin resistance, we examined auxin uptake using 1-cm root tips incubated in labeled auxin for 40 min. Our results clearly show that the uptake of [14C]2,4-D, [3H]NAA, [3H]IAA, and [3H]IBA was significantly reduced in roots of Lrt1 seedlings compared with wild type, suggesting that the resistance of Lrt1 roots to auxin is due to altered auxin uptake. Taken together, auxin influx carrier plays a critical role in regulating lateral root formation and root gravity response in rice.
