| Zinc finger protein plays important role in the plant development. They can recognize and bind specific DNA sequence to control the transcription. Furthermore, They are also involved in the regulation of protein-protein interaction. According to the sequence characterization of zinc finger protein and other transcription factors, 58 EST sequences were selected from EST database of a 10 K rice cDNA chips. Based on their tissue expression specificity, seven genes were selected and transformed into rice. By analyzing the phenotype of transgenic rice, it was found that these genes had distinct function in the development of rice. C1 gene modulated the plant height and development of spikes. The expression of F9 gene could affect the morphology of pistils and stamens. S34 gene was able to regulate the obliquity of leaves. F14 gene encoded a nuclear located TFIIIA zinc finger protein and its physiological function was still unknown. F35 transgenic rice plants generated shorter primary roots and reduced number of lateral roots. Furthermore, F35 gene encoded a putative ArfGAP. So, it was named as OsAGAP and further studied.The full-length cDNA of OsAGAP consisted of 1328 nucleotides. The protein encoded was composed by 320 amino acids and included two conserved domains: zinc finger domain and C2 domain. The zinc finger domain belonged to CX2CX16CX2C type, characteristic of ArfGAP domain. The result of GTPase activity assay showed that OsAGAP protein was able to activate the GTPase activity of rice Arf. Furthermore, OsAGAP could rescue the phenotype of yeast gcs1â–³ glo3 â–³ knock-out mutants. These results suggested that OsAGAP encoded an ArfGAP in rice.OsAGAP located in all of the organs. RNA in situ hybridization showed that it was expressed strongly in the stem meristem, lateral primordial and lateral roots. Its expression in the root tip was mainly limited to the central vascular tissues, cortical tissues and merismatic cells. The expression in the root tips correlated well with theauxin transport pathway. At the subcellular level, OsAGAP was located widely at the cell membrane, cytoplasm and nuclear.The OsAGAP overexpressing rice plants had shortened primary roots and adventitious roots, reduced number of lateral roots and abnormal gravitropism. The growth of primary roots in OsAGAP overexpressing rice was resistant to TIBA, IAA, and 2,4-D, but the sensitivity to NAA was consistent with wild type. The result suggested that OsAGAP overexpressing rice was defective of auxin influx. Auxin transport assay showed that the auxin transport in transgenic rice was reduced to one half of the wild type. Influx assay further showed that the carrier-mediated auxin influx was suppressed. In addition, NAA was able to rescue the reduced number of lateral roots and deficient gravitropism in overexpressing rice. So, overexpression of OsAGAP led to the reduction of auxin influx ability in rice.FM1-43 is a fluorescence dye that specially labels vesicle traffic in cells. After labeled by FM1-43, scratches of fluorescence were accumulated in OsAGAP overexpressing rice cells which was distinct from the fluorescent dots in wild type. The fluorescent scratches was named as "BFA (brefeldin A) compartment" that was typical of destroyed vesicle traffic. Observed with TEM, large number of small vacuoles with high electronic density of grains was accumulated in the overexpressing cells. It can be inferred that, as a result of disrupted vesicle traffic, the metabolite can't be transported properly or secreted outside. The metabolite was stored in the vacuoles so as to keep a stable cell environment.Study in yeasts and mammal cells showed, ArfGAP was an important factor that was involved in the regulation of vesicular transport. However, there's still no report about the physiological role of ArfGAP in plant metabolism. Our results showed that auxin polar transport, more precisely auxin influx, was regulated by OsAGAP through vesicle traffic mediation. So, it might be inferred that ArfGAP played a role in auxin polar transport.However, OsAGAP controlle...
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