[in Japanese]

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Monocot plants produce numerous adventitious (crown) roots that are dominant in the root system of cereals. It is known that root formation is promoted by auxin and suppressed by cytokinin, however, the molecular mechanism is still unknown. We are performing an analysis on crl1, crl4 and crl5 mutants defective in crown root initiation, the first step of its primordium formation. We revealed that CRL4/OsGNOM participates in polar auxin transport by regulating the recycle of auxin efflux carrier and mediates appropriate auxin accumulation to the basal portion of shoot and gradient in the region where crown root initiation occurs. It was also shown that CRL1/ARL1 and CRL5 may be directly up-regulated by an ARF in downstream of auxin signaling pathway and positively regulates crown root initiation. In addition to that, CRL5 promotes crown root initiation by suppressing cytokinin signaling, indicating that CRL5 plays an important role in mediating auxin signaling and cytokinin signaling.

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