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Characterizations of the uro Mutant Suggest that the URO Gene Is ...

Characterizations of the uro Mutant Suggest that the URO Gene Is ...

Characterizations of the uro Mutant Suggest that the URO Gene Is

Acta Botanica Sinica 2004, 46 (7): 846853 http://www.chineseplantscience.com Characterizations of the uro Mutant Suggest that the URO Gene Is Involved in the Auxin Action in Arabidopsis GUO Ying-Li 1, 2* , YUAN Zheng 1* , SUN Yue 1, 3** , LIU Jing 2 , HUANG Hai 1*** (1. State Key Laboratory of Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai 200032, China; 2. School of Life Sciences, University of Science and Technology of China, Hefei 230027, China; 3. College of Life Sciences, East China Normal University, Shanghai 200062, China) Abstract: The Arabidopsis gene UPRIGHT ROSETTE (URO) was previously identified as a leaf developmental regulator, as all rosette leaves of the semi-dominant upright rosette (uro) mutant grow uprightly at seedling stages. Here, we report more detailed phenotypic characterizations of the uro mutant and show that the URO gene has multiple functions in plant development. In addition to its aberrant leaf-growing pattern, the uro mutant displayed pleiotropic phenotypes. Both uro/+ and uro/uro plants showed a loss of apical dominance, while such a phenotype in the uro/uro plants appeared more severe. Some secondary branches of the uro/uro plants were replaced by leaves, for which petioles were attached to the abaxial side of leaves. Flowers often exhibited varying abnormalities, with altered numbers of petals and stamens and abnormally fused organs. Stems of the uro mutant were soft, which was caused by lacking interfascicular fiber. In addition, vascular differentiation in mutant stem was delayed. The loss of apical dominance and the defects in vascular development and interfascicular fiber formation suggest that the URO function might be associated with auxin-mediated plant development. To provide more direct evidence whether the URO is involved in auxin action, we examined the URO function in auxin polar transportation pathway by analyzing pinformed1 (pin1) uro double mutant. Phenotypes of the double mutant suggest that URO and PINFORMED1 (PIN1) have partial genetic interactions in plant development, which further supports the hypothesis that the URO gene may play an important role in the auxin regulatory pathway. Key words: Arabidopsis ; auxin; interfascicular fiber; pinformed1; upright rosette The plant hormone auxin plays a critical role in the regulation of plant growth and development, including cell divi- relevant mutants. secting auxin regulatory pathways by analyzing more novel sion and expansion, vascular tissue differentiation, root We reported in our previous work the identification of initiation, apical dominance, gravitropic and phototropic several Arabidopsis mutants that are defective in leaf development (Sun et al., 2000). One of these mutants, named responses, fruit ripening, leaf senescence, and abscission of leaves and fruits (Eckardt, 2001). In recent years, our upright rosette (uro) that was isolated from the T-DNAinsertional mutagenesis population, demonstrated abnor- understanding of auxin action in several research fields has been advanced, especially in the auxin polar transport, mal leaf growth pattern. Each rosette leaf at seedling stages auxin metabolism, molecular basis of gene responses to the had a smaller angle to the primary inflorescence stem than auxin, and auxin-directed protein degradation. In particular, that in the wild-type leaves. Genetic analysis demonstrated many genes that function in the auxin-related regulatory that the uro phenotype was caused by a semi-dominant pathways have been uncovered mainly by studies of auxindefective mutants, and the functional characterizations of short arm of chromosome 3, about 37 cM from telomere nuclear mutation, and the URO locus was mapped to the these genes provide new insights into the plant development (Kepinski and Leyser, 2002; Muday, 2002; Vogler and phenotypic characterizations of the uro mutant. In addi- (Sun et al., 2000). We report in this work the more detailed Kuhlemeier, 2003). It is widely expected that the forward tion to the abnormal leaf growth, the uro mutation results genetic approach will be very useful in the future in dis- in pleiotropic defects in the development of stem, Received 4 Nov. 2003 Accepted 2 Apr. 2004 Supported by the Hi-Tech Research and Development (863) Program of China (2001AA225031) and the National Natural Science Foundation of China (90208009). * Both authors contributed equally to this work. ** Author for correspondence. Tel: +86 (0)21 62431551; E-mail: . *** Author for correspondence. Tel: +86 (0)21 64042090; E-mail: .

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