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Xiao-Ming Feng, Yu Qiao, Ke Mao, Yu-Jin Hao and Chun-Xiang You

Overexpression of Arabidopsis AtmiR408 Gene in Tobacco

MicroRNA miR408 is predicted to target the transcripts for the copper proteins plantacyanin and laccase in Arabidopsis. In this study it was found that miR408 is present in tobacco also. Its accumulation was positively induced by copper deficiency, providing additional evidence for the important role of miR408 in plant responses to nutriment conditions. To examine the functions of miR408 in tobacco, transgenic tobacco lines containing the Arabidopsis AtmiR408 gene were created. Two transgenic lines with miR408 oversupply were chosen for functional characterization. The results showed that miR408 oversupply down-regulated the activities of antioxidant enzymes such as SOD, POD and CAT. As a result, transgenic lines exhibited altered chlorophyll content and seedling root growth, especially under high copper conditions. This suggests that miR408 accumulates in response to copper deficiency and influences plant growth by regulating antioxidant enzymes. It may be that miR408 exists and functions in tobacco in a conserved way similarly to miR408 in Arabidopsis.

Open access

Yu Qiao, Xiao-Ming Feng, Ze-Zhou Liu, Shuang-Shuang Wang, Yu-Jin Hao and Chun-Xiang You

Cloning and Expression Analysis of LeTIR1 in Tomato

The full-length cDNA of LeTIR1 gene was isolated from tomato with EST-based in silico cloning followed by RACE amplification. LeTIR1 contained an open reading frame (ORF) 1872 bp long, encoding 624 amino acid residues. The predicted protein LeTIR1 had one F-box motif and eleven leucine-rich repeats (LRRs), all of which are highly conserved in TIR1 proteins of other plant species. Phylogenetic analysis showed that the LeTIR1 protein shared high similarity with other known TIR1 proteins. Both sequence and phylogenetic analysis suggested that LeTIR1 is a TIR1 homologue and encodes an F-box protein in tomato. Semi-quantitative RT-PCR indicated that LeTIR1 was expressed constitutively in all organs tested, with higher expression in stem than root, leaf, flower and fruit. Its expression level was positively correlated with the auxin distribution in stem or axillary shoot, and was induced by spraying exogenous IAA.