ABSTRACT
Abbreviations ................................................................................................................................. 127 5.1 NAC Transcription Factors ................................................................................................... 128
5.1.1 Structure and Phylogenic Classification ................................................................... 128 5.2 Roles Played by NAC Transcription Factors ........................................................................ 131
5.2.1 Interaction between Host NAC and Viral Proteins .................................................. 131 5.3 Rice NAC Gene Response to Rice Viral Infection ............................................................... 131
5.3.1 Rice Dwarf Virus...................................................................................................... 131 5.3.2 Rice Stripe Virus ...................................................................................................... 137 5.3.3 Rice Tungro Spherical Virus .................................................................................... 137 5.3.4 Rice Grassy Stunt Virus ........................................................................................... 140
5.4 Comparison of Expression of NAC Genes in Response to Four Viral Infections ................ 143 5.5 Conclusion ............................................................................................................................ 149 Acknowledgments .......................................................................................................................... 149 References ...................................................................................................................................... 150
DEG Differentially expressed gene GLH Green leafhopper HR Hypersensitive response JA Jasmonic acid NAC NAM, ATAF1,2, CUC2, a multifunctional plant TF family NAM No apical meristem (NAM), an NAC gene involved in the develop-
ment of the shoot apical meristem PR protein Pathogenesis-related protein RDV Rice dwarf virus REn Replication Enhancer RGSV Rice grassy stunt virus RSV Rice stripe virus RTBV Rice tungro bacilliform virus RTD Rice tungro disease RTSV Rice tungro spherical virus SNAC Stress-responsive NAC TCV Turnip crinkle virus TF Transcription factor TLCV Tomato leaf curl virus TMV Tobacco mosaic virus WDV Wheat dwarf geminivirus
5.1 NAC TRANSCRIPTION FACTORS
Transcription factors (TFs) and the corresponding cis-elements in the promoter region of the transcription unit are important switches that regulate temporal and spatial gene expression. Genome sequence analysis of many species has identified many of the genes encoding transcription factors. The transcription factor NAC (no apical meristem [NAM], Arabidopsis transcription activation factor [ATAF], and cup-shaped cotyledon [CUC]) (Aida et al. 1997; Souer et al. 1996) is a superfamily of transcription factors that belongs to the helix-turn-helix protein family, which contains five groups of proteins that have basic (bHLH and bZIP), zinc coordinating factor, helixturn-helix, beta-scaffold (beta-ribbon), and other domain structures. Genes encoding NAC proteins are not found in bacteria, yeast, fungi, algae, or animal genomes, but are found in the genome of spike moss (Selaginella moellendorffii) and those of higher plants. Extensive investigation, aided by the availability of several complete plant genome sequences, has identified 117 NAC genes in Arabidopsis, 151 in rice, 79 in grape, 26 in citrus, 163 in poplar, and 152 each in soybean and tobacco (Hu et al. 2010; Le et al. 2011; Nuruzzaman et al. 2010, 2012b; Rushton et al. 2008).
