Polar auxin transport (PAT) is critical in plant growth and development, especially polar differentiation and pattern formation. Lots of studies have been performed in dicots while relative less in monocots. Using two...Polar auxin transport (PAT) is critical in plant growth and development, especially polar differentiation and pattern formation. Lots of studies have been performed in dicots while relative less in monocots. Using two kinds of PAT inhibitors, 2, 3, 5-triiodobenzoic acid (TIBA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA), it was shown that PAT is important for rice (Oryza sativa L. cv. Zhonghua 11) root development, including elongation of the primary roots, initiation and elongation of lateral roots, and formation of adventitious roots. Inhibition of PAT resulted in the shortened primary roots, less and shortened lateral and adventitious roots. Exogenously supplemented NAA can partially rescue the formation of adventitious roots but not lateral roots, while low concentration of NAA (0.1 mumol/L) could not rescue either of them, suggesting the possible different mechanisms of lateral and adventitious root initiations. Treatment of 30 mumol/L TIBA did not completely inhibit the initiation of lateral roots, and survival capacities of which were demonstrated through cross section experiments revealing the presence of primordial of lateral roots at different stages. Further studies through localized application of PAT inhibitors indicated that auxin flow, transported from coleoptiles to the base, is not only responsible for the auxin contents in stem nodes but also critical for initiation and elongation of adventitious roots.展开更多
In plants, proper seed development and the continuing post-embryonic organogenesis both require that dif- ferent cell types are correctly differentiated in response to internal and external stimuli. Among internal sti...In plants, proper seed development and the continuing post-embryonic organogenesis both require that dif- ferent cell types are correctly differentiated in response to internal and external stimuli. Among internal stimuli, plant hormones and particularly auxin and its polar transport （PAT） have been shown to regulate a multitude of plant phys- iological processes during vegetative and reproductive development. Although our current auxin knowledge is almost based on the results from researches on the eudicot Arabidopsis thaliana, during the last few years, many studies tried to transfer this knowledge from model to crop species, maize in particular. Applications of auxin transport inhibitors, mutant characterization, and molecular and cell biology approaches, facilitated by the sequencing of the maize genome, allowed the identification of genes involved in auxin metabolism, signaling, and particularly in polar auxin transport. PIN auxin efflux carriers have been shown to play an essential role in regulating PAT during both seed and post-embryonic development in maize. In this review, we provide a summary of the recent findings on PIN-mediated polar auxin transport during maize development. Similarities and differences between maize and Arabidopsis are analyzed and discussed, also considering that their different plant architecture depends on the differentiation of structures whose development is con- trolled by auxins.展开更多
The effects of auxin polar transport inhibitors, 9-hydroxy-fluorene-9-carboxylic acid (HFCA); 2, 3, 5-triiodobenzoic acid (TIBA) and trans-cinnamic acid (CA)on leaf pattern formation were investigated with shoots form...The effects of auxin polar transport inhibitors, 9-hydroxy-fluorene-9-carboxylic acid (HFCA); 2, 3, 5-triiodobenzoic acid (TIBA) and trans-cinnamic acid (CA)on leaf pattern formation were investigated with shoots formed from cultured leaf explants of tobacco and cultured pedicel explants of Orychophragmus violaceus, and the seedlings of tobacco and Brassica chinensis. Although the effective concentration varies with the inhibitors used, all of the inhibitors induced the formation of trumpet-shaped and/or fused leaves. The frequency of trumpet-shaped leaf formation was related to the concentration of inhibitors in the medium.Histological observation of tobacco seedlings showed that there was only one main vascular bundle and several minor vascular bundles in normal leaves of the control, but there were several vascular bundles of more or less the same size in the trumpet-shaped leaves of treated ones.These results indicated that auxin polar transport played an important role on bilateral symmetry of leaf growth.展开更多
Study on the role of quereentin in polar auxin transportation. Arabidopsis was cultured on medium supplemented with quereetin to observe the growth of hypoeotyls, ^14C-IAA transport assays were conducted to measure th...Study on the role of quereentin in polar auxin transportation. Arabidopsis was cultured on medium supplemented with quereetin to observe the growth of hypoeotyls, ^14C-IAA transport assays were conducted to measure the auxin transport activity. The results showed that Arabidopsis mutant auxl which had been deficient in auxin influx transportion obviously recovered the ability after eultured on the medium with quercetin. The polar auxin transport was promoted by the addition of quereetin. These results indicated that quereetin could promote polar auxin transport in vivo.展开更多
Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene fa...Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier (G(?)lweiler et al, 1998). Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpin1), which encoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level with AtPINl and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homology to AtPIN3). Hydrophobic analysis showed similar structures between BjPINl and AtPIN proteins. Presence of 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp) in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested, with a relatively higher level of transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains, young seeds, root tip, leaf vascular tissue and trace bundle, stem epidermis, cortex and vascular cells. BjPINl was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.展开更多
Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues from Brassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3 encoded proteins contai...Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues from Brassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3 encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities with each other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BJPIN2 and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 was expressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls. Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' technique using primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven by Bjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein, epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with different expression patterns in B. juncea suggested the presence of a gene family.展开更多
Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene fa...Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier (G(?)lweiler et al, 1998). Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpin1), which encoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level with AtPINl and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homology to AtPIN3). Hydrophobic analysis showed similar structures between BjPINl and AtPIN proteins. Presence of 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp) in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested, with a relatively higher level of transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains, young seeds, root tip, leaf vascular tissue and trace bundle, stem epidermis, cortex and vascular cells. BjPINl was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.展开更多
Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containi...Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities witheach other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BjPIN2and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 wasexpressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' techniqueusing primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven byBjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein,epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with differentexpression patterns in B. juncea suggested the presence of a gene family.展开更多
The auxin polar transporter,PIN-FORMED 2(PIN2)plays an important role in root development.However,it remains unclear whether PIN2 genes form two Liriodendron species,L.chinense(LcPIN2)and L.tulipifera(LtPIN2),are both...The auxin polar transporter,PIN-FORMED 2(PIN2)plays an important role in root development.However,it remains unclear whether PIN2 genes form two Liriodendron species,L.chinense(LcPIN2)and L.tulipifera(LtPIN2),are both involved in root development and whether and to what extent these two genes diverge in function.Here,we cloned and overexpressed LcPIN2 and LtPIN2 in Arabidopsis thaliana wild-type(WT)and Atpin2 mutant.Phylogenetic and sequence analysis showed a small degree of differentiation between these two Liriodendron PIN2 genes.Tissue-specific gene expression analysis indicated that both Liriodendron PIN2 genes were highly expressed in roots,implying a potential role in root development.Finally,heterologous overexpression of LcPIN2 and LtPIN2 in Arabidopsis both significantly increased the root length compared to wild-type and empty vector.Furthermore,the root length defect in Atpin2 was complemented both by LcPIN2 and LtPIN2.However,heterologous overexpression of LcPIN2 and LtPIN2 cannot rescue the defect in root gravitropism of Atpin2 mutants.Taken together,ourfindings unravel PIN2 genes from the magnoliids plant Liriodendron were functionally conserved with AtPIN2 in the dicotyledonous plant Arabidopsis in regard to the regulation of root length,but not root gravitropism.This study also provides a potential target for genetic improvement of the root system in these valuable forest trees Liriodendron.展开更多
The fibrous root system in cereals comprises primarily adventitious roots （ARs）, which play important roles in nutrient and water uptake. Current knowledge regarding the molecular mechanism underlying AR development...The fibrous root system in cereals comprises primarily adventitious roots （ARs）, which play important roles in nutrient and water uptake. Current knowledge regarding the molecular mechanism underlying AR development is still limited. We report here the isolation of four rice （Oryza sativa L.） mutants, from different genetic backgrounds, all of which were defective in AR formation. These mutants exhibited reduced numbers of lateral roots （LRs） and partial loss of gravitropism. The mutants also displayed enhanced sensitivity to N-l-naphthylphthalamic acid, an inhibitor of polar auxin transport （PAT）, indicating that the mutations affected auxin transport. Positional cloning using one of the four mutants revealed that it was caused by loss-of-function of a guanine nucleotide exchange factor for ADP- ribosylation factor （OsGNOM1）. RT-PCR and analysis of promoter：：GUS transgenic plants showed that OsGNOM1 is expressed in AR primordia, vascular tissues, LRs, root tips, leaves, anthers and lemma veins, with a distribution pattern similar to that of auxin. In addition, the expressions of OsPIN2, OsPIN5b and OsPIN9 were altered in the mutants. Taken together, these findings indicate that OsGNOM1 affects the formation of ARs through regulating PAT.展开更多
文摘Polar auxin transport (PAT) is critical in plant growth and development, especially polar differentiation and pattern formation. Lots of studies have been performed in dicots while relative less in monocots. Using two kinds of PAT inhibitors, 2, 3, 5-triiodobenzoic acid (TIBA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA), it was shown that PAT is important for rice (Oryza sativa L. cv. Zhonghua 11) root development, including elongation of the primary roots, initiation and elongation of lateral roots, and formation of adventitious roots. Inhibition of PAT resulted in the shortened primary roots, less and shortened lateral and adventitious roots. Exogenously supplemented NAA can partially rescue the formation of adventitious roots but not lateral roots, while low concentration of NAA (0.1 mumol/L) could not rescue either of them, suggesting the possible different mechanisms of lateral and adventitious root initiations. Treatment of 30 mumol/L TIBA did not completely inhibit the initiation of lateral roots, and survival capacities of which were demonstrated through cross section experiments revealing the presence of primordial of lateral roots at different stages. Further studies through localized application of PAT inhibitors indicated that auxin flow, transported from coleoptiles to the base, is not only responsible for the auxin contents in stem nodes but also critical for initiation and elongation of adventitious roots.
文摘In plants, proper seed development and the continuing post-embryonic organogenesis both require that dif- ferent cell types are correctly differentiated in response to internal and external stimuli. Among internal stimuli, plant hormones and particularly auxin and its polar transport （PAT） have been shown to regulate a multitude of plant phys- iological processes during vegetative and reproductive development. Although our current auxin knowledge is almost based on the results from researches on the eudicot Arabidopsis thaliana, during the last few years, many studies tried to transfer this knowledge from model to crop species, maize in particular. Applications of auxin transport inhibitors, mutant characterization, and molecular and cell biology approaches, facilitated by the sequencing of the maize genome, allowed the identification of genes involved in auxin metabolism, signaling, and particularly in polar auxin transport. PIN auxin efflux carriers have been shown to play an essential role in regulating PAT during both seed and post-embryonic development in maize. In this review, we provide a summary of the recent findings on PIN-mediated polar auxin transport during maize development. Similarities and differences between maize and Arabidopsis are analyzed and discussed, also considering that their different plant architecture depends on the differentiation of structures whose development is con- trolled by auxins.
文摘The effects of auxin polar transport inhibitors, 9-hydroxy-fluorene-9-carboxylic acid (HFCA); 2, 3, 5-triiodobenzoic acid (TIBA) and trans-cinnamic acid (CA)on leaf pattern formation were investigated with shoots formed from cultured leaf explants of tobacco and cultured pedicel explants of Orychophragmus violaceus, and the seedlings of tobacco and Brassica chinensis. Although the effective concentration varies with the inhibitors used, all of the inhibitors induced the formation of trumpet-shaped and/or fused leaves. The frequency of trumpet-shaped leaf formation was related to the concentration of inhibitors in the medium.Histological observation of tobacco seedlings showed that there was only one main vascular bundle and several minor vascular bundles in normal leaves of the control, but there were several vascular bundles of more or less the same size in the trumpet-shaped leaves of treated ones.These results indicated that auxin polar transport played an important role on bilateral symmetry of leaf growth.
基金Key Project of Conditions Platform of National Science and Technology (2005DKA21002-15)~~
文摘Study on the role of quereentin in polar auxin transportation. Arabidopsis was cultured on medium supplemented with quereetin to observe the growth of hypoeotyls, ^14C-IAA transport assays were conducted to measure the auxin transport activity. The results showed that Arabidopsis mutant auxl which had been deficient in auxin influx transportion obviously recovered the ability after eultured on the medium with quercetin. The polar auxin transport was promoted by the addition of quereetin. These results indicated that quereetin could promote polar auxin transport in vivo.
基金Studies were supported by "the National NaturalScience Foundation of China, No. 30070073", StateKey Project of Basic Research, No. G199901l604"and "National Natural Science Foundation of Pan-Deng". We thank Dr. Charles Brearley and JianXu for hel
文摘Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier (G(?)lweiler et al, 1998). Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpin1), which encoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level with AtPINl and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homology to AtPIN3). Hydrophobic analysis showed similar structures between BjPINl and AtPIN proteins. Presence of 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp) in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested, with a relatively higher level of transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains, young seeds, root tip, leaf vascular tissue and trace bundle, stem epidermis, cortex and vascular cells. BjPINl was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.
基金Studies were supported by the National NaturalSciences Foundation of China (No. 30070073, 95-Yu-29-7) and State Key Project of Basic Research (No.G1999011604). We greatly thank Dr. K1aus Palme for providing the Atpinl nucleotide sequences.
文摘Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues from Brassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3 encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities with each other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BJPIN2 and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 was expressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls. Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' technique using primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven by Bjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein, epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with different expression patterns in B. juncea suggested the presence of a gene family.
基金Studies were supported by 'the National NaturalScience Foundation of China, No. 30070073', StateKey Project of Basic Research, No. G199901l604'and 'National Natural Science Foundation of Pan-Deng'. We thank Dr. Charles Brearley and JianXu for hel
文摘Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier (G(?)lweiler et al, 1998). Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpin1), which encoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level with AtPINl and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homology to AtPIN3). Hydrophobic analysis showed similar structures between BjPINl and AtPIN proteins. Presence of 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp) in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested, with a relatively higher level of transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains, young seeds, root tip, leaf vascular tissue and trace bundle, stem epidermis, cortex and vascular cells. BjPINl was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.
文摘Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities witheach other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BjPIN2and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 wasexpressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' techniqueusing primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven byBjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein,epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with differentexpression patterns in B. juncea suggested the presence of a gene family.
基金supported by the Youth Foundation of the Natural Science Foundation of Jiangsu Province(BK20210614)the Nature Science Foundation of China(32071784)+1 种基金Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX21_0921).
文摘The auxin polar transporter,PIN-FORMED 2(PIN2)plays an important role in root development.However,it remains unclear whether PIN2 genes form two Liriodendron species,L.chinense(LcPIN2)and L.tulipifera(LtPIN2),are both involved in root development and whether and to what extent these two genes diverge in function.Here,we cloned and overexpressed LcPIN2 and LtPIN2 in Arabidopsis thaliana wild-type(WT)and Atpin2 mutant.Phylogenetic and sequence analysis showed a small degree of differentiation between these two Liriodendron PIN2 genes.Tissue-specific gene expression analysis indicated that both Liriodendron PIN2 genes were highly expressed in roots,implying a potential role in root development.Finally,heterologous overexpression of LcPIN2 and LtPIN2 in Arabidopsis both significantly increased the root length compared to wild-type and empty vector.Furthermore,the root length defect in Atpin2 was complemented both by LcPIN2 and LtPIN2.However,heterologous overexpression of LcPIN2 and LtPIN2 cannot rescue the defect in root gravitropism of Atpin2 mutants.Taken together,ourfindings unravel PIN2 genes from the magnoliids plant Liriodendron were functionally conserved with AtPIN2 in the dicotyledonous plant Arabidopsis in regard to the regulation of root length,but not root gravitropism.This study also provides a potential target for genetic improvement of the root system in these valuable forest trees Liriodendron.
基金Acknowledgments This work was supported by the Key Basic Research Special Foundation of China （2005CB20900）, the National High Technology Research and Development Program （2007AA021403, 2006AA10Z 175）, the National Natural Science Foundation of China （30471118 and 30770191） and the Specialized Research Fund for the Doctoral Program of Higher Education （20070335081）.
文摘The fibrous root system in cereals comprises primarily adventitious roots （ARs）, which play important roles in nutrient and water uptake. Current knowledge regarding the molecular mechanism underlying AR development is still limited. We report here the isolation of four rice （Oryza sativa L.） mutants, from different genetic backgrounds, all of which were defective in AR formation. These mutants exhibited reduced numbers of lateral roots （LRs） and partial loss of gravitropism. The mutants also displayed enhanced sensitivity to N-l-naphthylphthalamic acid, an inhibitor of polar auxin transport （PAT）, indicating that the mutations affected auxin transport. Positional cloning using one of the four mutants revealed that it was caused by loss-of-function of a guanine nucleotide exchange factor for ADP- ribosylation factor （OsGNOM1）. RT-PCR and analysis of promoter：：GUS transgenic plants showed that OsGNOM1 is expressed in AR primordia, vascular tissues, LRs, root tips, leaves, anthers and lemma veins, with a distribution pattern similar to that of auxin. In addition, the expressions of OsPIN2, OsPIN5b and OsPIN9 were altered in the mutants. Taken together, these findings indicate that OsGNOM1 affects the formation of ARs through regulating PAT.
