The Wheat NAC Transcription Factor TaNAC2L Is Regulated at the Transcriptional and Post-Translational Levels and Promotes Heat Stress Tolerance in Transgenic Arabidopsis

<div><p>Heat stress poses a serious threat to global crop production. In efforts that aim to mitigate the adverse effects of heat stress on crops, a variety of genetic tools are being used to develop plants with improved thermotolerance. The characterization of important regulators of heat stress tolerance provides essential information for this aim. In this study, we examine the wheat (<i>Triticum aestivum</i>) NAC transcription factor gene <i>TaNAC2L</i>. High temperature induced <i>TaNAC2L</i> expression in wheat and overexpression of <i>TaNAC2L</i> in <i>Arabidopsis thaliana</i> enhanced acquired heat tolerance without causing obvious alterations in phenotype compared with wild type under normal conditions. <i>TaNAC2L</i> overexpression also activated the expression of heat-related genes in the transgenic Arabidopsis plants, suggesting that TaNAC2L may improve heat tolerance by regulating the expression of stress-responsive genes. Notably, TaNAC2L is also regulated at the post-translational level and might be degraded via a proteasome-mediated pathway. Thus, this wheat transcription factor may have potential uses in enhancing thermotolerance in crops.</p></div

The frequency of conserved miRNAs present in the sequenced small RNA library

<p><b>Copyright information:</b></p><p>Taken from "Cloning and characterization of microRNAs from wheat (L.)"</p><p>http://genomebiology.com/2007/8/6/R96</p><p>Genome Biology 2007;8(6):R96-R96.</p><p>Published online 1 Jun 2007</p><p>PMCID:PMC2394755.</p><p></p

Expression of six stress marker genes in <i>TaNAC2L</i> transgenic Arabidopsis plants and wild type (WT) under normal and heat stress conditions.

<p>The transcript levels of <i>DREB2A</i>, <i>DREB2B</i>, <i>AtCYP18-1</i>, <i>RD17</i>, <i>HSP26</i>.<i>5</i>, <i>LEA</i>, <i>AtGolS1</i>, <i>HSP70</i>, <i>AtHsfA3</i>, and <i>RD29A</i> were determined by quantitative RT-PCR. Values represent the mean ± SD of three independent experiments and were normalized to <i>ACTIN</i>.</p

Hypocotyl elongation of <i>TaNAC2L</i>-overexpressing transgenic Arabidopsis plants.

<p>A. Levels of the <i>TaNAC2L</i> transcript in the wild type (WT) and 20 transgenic Arabidopsis lines according to real-time quantitative PCR analyses. B. Hypocotyl elongation of WT and transgenic plants (#13) after growth for 2.5 days in the dark at 22°C. Seedling treatments included: 1) maintained at 22°C; 2) treated at 38°C for 90 min; 3) treated at 45°C for 2 h; 4) first treated at 38°C for 90 min followed by 2 h at 22°C and then 2 h at 45°C. For all treatments, seedlings were returned to 22°C for 2.5 days and then photographed. The quantitative analysis of the hypocotyl length of the wild-type and transgenic plants is presented below the photographs.</p

Transcript and protein levels of TaNAC2L in the <i>drip1 drip2</i> double mutant background.

<p><i>TaNAC2L</i> was highly transcribed in three independent siblings of <i>TaNAC2L</i>-overexpressed lines crossed with the <i>drip1 drip2</i> double mutant; the absence of DRIP1 and DRIP2 failed to block the degradation of the TaNAC2L protein.</p

Protein levels of TaNAC2L in <i>TaNAC2L-OX</i> transgenic lines.

<p>A. TaNAC2L protein and transcript levels in <i>TaNAC2L</i>-overexpressing lines (#2, #9 and #13) under normal conditions and 38°C heat stress. Western blot analyses were performed with the anti-HA monoclonal antibody. B. Seven-day-old wild-type (WT) and <i>TaNAC2L-OX</i>-#13 seedlings were treated at 38°C for 2 h. After heat treatment, seedlings were transferred to dimethylsulfoxide (DMSO) for 0.5, 1, 2, 3, 4, 6, or 8 h; or DMSO with 50 μM MG132 for 1, 3, 4, 6, 8, 12, or 24 h before harvesting. The HA antibody was used for the immunoblot analyses.</p

Supplemental Dataset

Supplemental Datase

Seed germination rate of maize hybrid Zong3/87-1 and its parents.

<p>HAI, hours after imbibitions *, represent Significance level <i>p</i><0.05; ** represent Significance level <i>p</i><0.01.</p

Analysis of actin expression during germination of maize dry and 24 h imbibed seeds embryos at the protein level shown by western immunoblotting with monoclonal antibodies MabGpa.

<p>A, The presence of actin isoforms in the maize embryo was analysed by 2-DE. B, Western immunoblotting detected the 42 kDa actin. Equivalent amounts of protein (20 µg) were loaded. C, Protein profile obtained on a 12.5% polyacrylamide gel stained with Coomassie Brilliant Blue. DS, dry seed; 24 HAI, 24 hours after imbibitions.</p

The differentially expressed protein spots of additive and nonadditive between maize hybrid and its parental lines.

a)<p>DS, dry seed; 24 HAI, 24 hours after imbibitions;</p>b)<p>++: above high parent expression;</p>c)<p>+: high parent expression;</p>d)<p>+/−: partial dominance expression;</p>e)<p>D: different from additivity (midparent value), not belonging to any of the other classes;</p>f)<p>−: low parent expression;</p>g)<p>−−: Below low parent expression.</p