We previously reported that arf8-1, a semidominant T-DNA insertion line of ARF8 gene, showed a long-hypocotyl phenotype when grown in white light. However, no report mentioned the similar phenotype in other mutant lines of ARFS. Through phenotypic and genetic analyses on hypocityl length of different mutant lines of ARF8 and NPH4/ARF7 gene, origin of long-hypocotyl phenotype in arf8-1, nph4-102 and nph4-107 has been probed. Here we reported that arfd-2, arf8-3 and arf8-4 indeed display same hypocotyls length with corre- sponding wild type. Among mutant lines of NPH4/ARF7 gene, nph4-102 and nph4-107 showed long-hypocotyl phenotype, too. Also, F1 of Col crossing with nph4-102 and nph4-107 show middle length of hypocotyl between wild type and mutant, meaning that they are semidominant, too. Hypocotyl length of double mutant arf8-1 nph4-102 is longer than each single mutant, indicating the independent action between arf8-1 and nph4-102 in controlling elongation of hypocotyls. Genomic sequence analyses showed the mutation sites of arf8-1, nph4-102 and nph4-107 are at the top of DNA bind domain in ARF8 and NPH4/ARF7 and may give rise to similar truncate proteins including part of hypocotyl phenotype of aft＇d-l, of ARF8 gene or NPH4/ARF7 DNA bind domain of related genes. nph4-102 and nph4-107 results from gene Therefore, it is most possible that the long the truncate proteins but not loss-of-function%通过对拟南芥（Arabidopsis thaliana）ARF8和NPH4／ARF7基因的突变体以及有关双突变体的下胚轴长度的表型和遗传分析，探讨了arf8—1、nph4—102和nph4—107长下胚轴表型的起源．结果表明，ARF8基因的其他突变体arf8—2、arf8—3和arf8-4都没有表现出类似于。arf8-1的长下胚轴表型；在与ARF8同源性较高的NPH4／ARF7的突变体中，突变位点与arf8-J相似的nph4—102和nph4—107表现出与aoOd一，相似的长下胚轴表型和不完全显性的遗传方式；双突变体arf8-J nph4—102的下胚轴长度比两个单突变体的长，说明arf8-J与nph4—102在长下胚轴表型上存在加性效应．因此，arf8-J、nph4—102和nph4—107的长下胚轴表型极可能源于相应突变体蛋白的产生，而非相关基因功能的缺失．
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