WRKY family proteins are a class of plant specific transcription factors that involve in many stress response pathways. It has been shown that one Arabidopsis WRKY protein, AtWRKY29/22, is activated by MAP kinase sign...WRKY family proteins are a class of plant specific transcription factors that involve in many stress response pathways. It has been shown that one Arabidopsis WRKY protein, AtWRKY29/22, is activated by MAP kinase signaling cascade and confers resistance to both bacterial and fungal pathogens. However, little is known about the biological roles of WRKY proteins in rice. In this study, we investigated the expression patterns of rice AtWRKY29/22 homolog, OsWRKY03, under different conditions, and also its possible role involved in plant defense. Our results showed that OsWRKY03 was up-regulated by several defense signaling molecules or different treatments. Further analysis revealed that the expression of OsWRKY03 was light dependent. Transcriptional activation activity of OsWRKY03 was also demonstrated by yeast functional assay. Transient expression of OsWRKY03-GFP fusion protein in onion epidermis cells showed that OsWRKY03 was a nuclear localized protein. OsNPR1 as well as several other pathogenesis-related genes, such as OsPRlb, phenylalanine ammonia-lyase （ZB8） and peroxidase （POX22.3）, were induced in OsWRKYO3-overexpressing transgenic plants. These results indicated that OsWRKY03 is located upstream of OsNPR 1 as a transcriptional activator in salicylic acid （SA）-dependent or jasmonic acid （JA）-dependent defense signaling cascades.展开更多
The plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin resp...The plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin response mutants in Arabidopsis. In addition, microRNAs （miRNAs） have been shown to be critical regulators of genes important for normal plant development and physiology. However, little is known about possible interactions between miRNAs and hormonal signaling during normal development. Here we show that an Arabidopsis microRNA, miR167, which has a complementary sequence to a portion of the A UXINRESPONSE FACTOR6 （ARF6） and ARF8 mRNAs, can cause transcript degradation for ARF8, but not for ARF6. We report phenotypic characterizations of 35S：：MIR167b transgenic lines, and show that severe 35S：：MIR167b transgenic lines had phenotypes similar to those of an arf6 arf8 double mutant. The transgenic phenotypes suggest that miR167 may repress ARF6 at the level of translation. We demonstrate that the transgenic plants are defective in all four whods of floral organs. In the transgenic flowers, filaments were abnormally short, anthers could not properly release pollen, and pollen grains did not germinate. Our results provide an important link between the miRNA-mediated regulatory pathway of gene expression and the auxin signaling network promoting plant reproductive development.展开更多
Light and the plant hormone ethylene regulate many aspects of plant growth and development in an overlapping and interdependent fashion. Little is known regarding how their signal transduction pathways cross-talk to r...Light and the plant hormone ethylene regulate many aspects of plant growth and development in an overlapping and interdependent fashion. Little is known regarding how their signal transduction pathways cross-talk to regulate plant development in a coordinated manner. Here, we report functional characterization of an AP2/DREB-type transcription factor, Arabidopsis RAP2.4, in mediating light and ethylene signaling. Expression of the RAP2.4 gene is down-regulated by light but up-regulated by salt and drought stresses. RAP2.4 protein is constitutively targeted to the nucleus and it can bind to both the ethylene-responsive GCC-box and the dehydration-responsive element （DRE）. We show that RAP2.4 protein possesses an intrinsic transcriptional activation activity in yeast cells and that it can activate a reporter gene driven by the DRE cis-element in Arabidopsis protoplasts. Overexpression of RAP2.4 or mutation in RAP2.4 cause altered expression of representative light-, ethylene-, and drought-responsive genes. Although no salient phenotype was observed with a rap2.4 loss-of-function mutant, constitutive overexpression of RAP2.4 results in defects in multiple developmental processes regulated by light and ethylene, including hypocotyl elongation and gravitropism, apical hook formation and cotyledon expansion, flowering time, root elongation, root hair formation, and drought tolerance. Based on these observations, we propose that RAP2.4 acts at or downstream of a converging point of light and ethylene signaling pathways to coordinately regulate multiple developmental processes and stress responses.展开更多
文摘WRKY family proteins are a class of plant specific transcription factors that involve in many stress response pathways. It has been shown that one Arabidopsis WRKY protein, AtWRKY29/22, is activated by MAP kinase signaling cascade and confers resistance to both bacterial and fungal pathogens. However, little is known about the biological roles of WRKY proteins in rice. In this study, we investigated the expression patterns of rice AtWRKY29/22 homolog, OsWRKY03, under different conditions, and also its possible role involved in plant defense. Our results showed that OsWRKY03 was up-regulated by several defense signaling molecules or different treatments. Further analysis revealed that the expression of OsWRKY03 was light dependent. Transcriptional activation activity of OsWRKY03 was also demonstrated by yeast functional assay. Transient expression of OsWRKY03-GFP fusion protein in onion epidermis cells showed that OsWRKY03 was a nuclear localized protein. OsNPR1 as well as several other pathogenesis-related genes, such as OsPRlb, phenylalanine ammonia-lyase （ZB8） and peroxidase （POX22.3）, were induced in OsWRKYO3-overexpressing transgenic plants. These results indicated that OsWRKY03 is located upstream of OsNPR 1 as a transcriptional activator in salicylic acid （SA）-dependent or jasmonic acid （JA）-dependent defense signaling cascades.
文摘The plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin response mutants in Arabidopsis. In addition, microRNAs （miRNAs） have been shown to be critical regulators of genes important for normal plant development and physiology. However, little is known about possible interactions between miRNAs and hormonal signaling during normal development. Here we show that an Arabidopsis microRNA, miR167, which has a complementary sequence to a portion of the A UXINRESPONSE FACTOR6 （ARF6） and ARF8 mRNAs, can cause transcript degradation for ARF8, but not for ARF6. We report phenotypic characterizations of 35S：：MIR167b transgenic lines, and show that severe 35S：：MIR167b transgenic lines had phenotypes similar to those of an arf6 arf8 double mutant. The transgenic phenotypes suggest that miR167 may repress ARF6 at the level of translation. We demonstrate that the transgenic plants are defective in all four whods of floral organs. In the transgenic flowers, filaments were abnormally short, anthers could not properly release pollen, and pollen grains did not germinate. Our results provide an important link between the miRNA-mediated regulatory pathway of gene expression and the auxin signaling network promoting plant reproductive development.
基金We thank Dr Jungmook Kim （Chonnam National University, Korea） for sharing the 4x DRE：：GUS reporter construct （Kim et al., 2002）. We also thank Erica Fishel and Ling Xu for technical assistance during this work. We thank Zhi-Liang Zheng （Lehman College, City University of New York）, Pradeep Kachroo （University of Kentucky）, and Elizabeth Estabrook （Boyce Thompson Institute） for their read- ing and comments on the manuscript. Thanks are also due to ABRC for distributing seeds and cDNA clones. This research was partially supported by set-up funds from Boyce Thompson Institute, Triad Foundation, and National Science Foundation （MCB-0420932 and IOS-0641639） to H.W.
文摘Light and the plant hormone ethylene regulate many aspects of plant growth and development in an overlapping and interdependent fashion. Little is known regarding how their signal transduction pathways cross-talk to regulate plant development in a coordinated manner. Here, we report functional characterization of an AP2/DREB-type transcription factor, Arabidopsis RAP2.4, in mediating light and ethylene signaling. Expression of the RAP2.4 gene is down-regulated by light but up-regulated by salt and drought stresses. RAP2.4 protein is constitutively targeted to the nucleus and it can bind to both the ethylene-responsive GCC-box and the dehydration-responsive element （DRE）. We show that RAP2.4 protein possesses an intrinsic transcriptional activation activity in yeast cells and that it can activate a reporter gene driven by the DRE cis-element in Arabidopsis protoplasts. Overexpression of RAP2.4 or mutation in RAP2.4 cause altered expression of representative light-, ethylene-, and drought-responsive genes. Although no salient phenotype was observed with a rap2.4 loss-of-function mutant, constitutive overexpression of RAP2.4 results in defects in multiple developmental processes regulated by light and ethylene, including hypocotyl elongation and gravitropism, apical hook formation and cotyledon expansion, flowering time, root elongation, root hair formation, and drought tolerance. Based on these observations, we propose that RAP2.4 acts at or downstream of a converging point of light and ethylene signaling pathways to coordinately regulate multiple developmental processes and stress responses.
