Guohui Yang

Overexpression of a Malus xiaojinensis Nas1 Gene Influences Flower Development and Tolerance to Iron Stress in Transgenic Tobacco

Iron (Fe) is one of the essential micronutrients required by all living organisms. Expression of MxNas1 of Malus xiaojinensis is enriched in active tissues, including leaves, roots, and phloem, and these seedlings are highly affected by Fe stress and indoleacetic acid treatment, but weakly affected by abscisic acid treatment. Subcellular localization has revealed that MxNas1 is preferentially localized in cell membranes. When this gene is introduced into tobacco, it promotes synthesis of nicotianamine (NA) synthase and increases NA content. Overexpression of MxNas1 improves tolerance to Fe stress in transgenic tobacco, but also leads to misshapen flowers. Higher levels of MxNas1 expression in transgenic tobacco plants also contributes to delayed flowering and increased levels of Fe and Zn in flowers. In addition to its role in metal transport in plants, NA may be involved in the regulation of metal transfer within cells. These results suggest that NA excess influences functions of metal-requiring proteins, including some of the transcription factors.

Isolation and characterization of MbWRKY2 gene involved in enhanced drought tolerance in transgenic tobacco

ABSTRACT Plant-specific WRKY transcription factors are widely involved in abiotic stress responses. In this study, a WRKY gene was isolated from Malus baccata (L.) Borkh and designated it as MbWRKY2. Subcellular localization showed that MbWRKY2 was localized in the nucleus. The expression levels of MbWRKY2 were up-regulated by abiotic stresses in M. baccata. When MbWRKY2 was introduced into tobacco, it improved drought stress tolerance in transgenic plants. The transgenic tobaccos had the higher contents of chlorophyl, proline, relative water content, AsA, and GSH, increased activities of CAT, APX, SOD, and POD, and decreased levels of MDA, H2O2, and electrolyte leakage than wild-type, especially when dealt with dehydration treatment. Moreover, the MbWRKY2-OE plants enhanced the expression of oxidative stress response and stress-related genes involved in osmotic adjustment and membrane protection. These results suggest that MbWRKY2 gene plays a positive regulatory role in drought stress response.

Molecular cloning and functional analysis of MbWRKY3 involved in improved drought tolerance in transformed tobacco

ABSTRACT Plant-specific WRKY transcription factors were involved in stress responses and ABA signaling. In the present study, a WRKY gene is isolated from Malus baccata (L.) Borkh and designated as MbWRKY3. Subcellular localization revealed that MbWRKY3 was localized onto nucleus. The MbWRKY3 expression levels were up-regulated by salinity, drought, and ABA treatments in M. baccata. When MbWRKY3 was introduced into tobaccos, it improved drought stress tolerance in transgenic plants. Compared to WT, the transgenic tobaccos had the higher levels of relative water content, and proline and chlorophyll contents, decreased levels of electrolyte leakage, MDA, and H2O2, increased activities of the reactive oxygen species-related enzymes (SOD, CAT, and POD), and greater up-regulations of the corresponding genes (NtSOD, NtCAT, and NtPOD), especially when dealt with drought stress. These results suggest that MbWRKY3 gene plays a positive regulatory role in drought stress response.

Isolation and functional analysis of MxNAS3 involved in enhanced iron stress tolerance and abnormal flower in transgenic Arabidopsis

ABSTRACT Metal trace elements, such as Fe, Zn, and Mn, are necessary micronutrients required by all plants. In this study, the MxNAS3 gene was cloned from Malus xiaojinensis and MxNAS3 was localized in the cytoplasmic membrane. The expression level of MxNAS3 in root and new leaf was higher than in mature leaf and phloem, which was greatly influenced by high and low Fe stresses, IAA and ABA treatments in M. xiaojinensis. Over-expression of MxNAS3 in transgenic Arabidopsis thaliana contributed to enhanced Fe stress tolerance, as well as higher levels of root length, fresh weight, concentrations of chlorophyll, nicotianamine, Fe, Zn, and Mn, especially under high and low Fe stresses. More importantly, it was the first time for us to find that higher expression of MxNAS3 in transgenic A. thaliana contributed to misshappen flowers. Moreover, the MxNAS5-OE A. thaliana had increased expression levels of flowering-related genes (AtYSL1, AtYSL3, AtAFDL, AtAP1, ATMYB21, and AtSAP).

Isolation and functional analysis of MdNAS1, with functions in improved iron stress tolerance and abnormal flower in transgenic tobacco

ABSTRACT Metal elements are essential micronutrients required by all plants for natural physiological activities. Nicotianamine is considered as the chelate substance in the transport of metal ions. In the present study, a new gene encoding NA synthase was isolated from Malus domestica (L.) Borkh and designated as MdNAS1. The expression levels of MdNAS1 were enriched in leaf, and phloem which were highly affected by Fe stress, indoleacetic acid (IAA) and abscisic acid (ABA) treatments in M. domestica seedlings. Subcellular localization research revealed that MdNAS1 was localized in cytoplasmic membrane. Overexpression of MdNAS1 in transgenic tobaccos increased the tolerance to Fe stress, but also contributes to higher chlorophyll, NA, Fe, Mn, Cu and Zn contents and abnormal flowers. Moreover, the MdNAS1-OE tobaccos had the increased expression levels of Fe uptake and transport related genes (NtFRO, NtIRT1, NtVIT, NtNRAMP1, and NtYSL).