In the complex family of heat stress transcription factors, HsfA1 has a unique role as master regulator of thermotolerance in tomato.
We generated transgenic tomato plants with altered expression of heat stress transcription factor HsfA1. Plants with 10-fold overexpression of HsfA1 (OE plants) were characterized by a single HsfA1 transgene cassette, whereas plants harboring a tandem inverted repeat of the cassette showed cosuppression (CS plants) by posttranscriptional silencing of the HsfA1 gene connected with formation of small interfering RNAs. Under normal growth conditions, major developmental parameters were similar for wild-type (WT), OE, and CS plants. However, CS plants and fruits were extremely sensitive to elevated temperatures, because heat stress-induced synthesis of chaperones and Hsfs was strongly reduced or lacking. Despite the complexity of the plant Hsf family with at least 17 members in tomato, HsfA1 has a unique function as master regulator for induced thermotolerance. Using transient reporter assays with mesophyll protoplasts from WT tomato, we demonstrated that plasmid-encoded HsfA1 and HsfA2 were well expressed. However, in CS protoplasts the cosuppression phenomenon was faithfully reproduced. Only transformation with HsfA2 expression plasmid led to normal expression of the transcription factor and reporter gene activation, whereas even high amounts of HsfA1 expression plasmids were silenced. Thermotolerance in CS protoplasts was restored by plasmid-borne HsfA2, resulting in expression of chaperones, thermoprotection of firefly luciferase, and assembly of heat stress granules.
Mishra
Shravan Kumar
SK
Biocenter of the Goethe University, D-60439 Frankfurt am Main, Germany.
Tripp
Joanna
J
Winkelhaus
Sybille
S
Tschiersch
Bettina
B
Theres
Klaus
K
Nover
Lutz
L
Scharf
Klaus-Dieter
KD
D015152:Blotting, Northern; D015139:Blotting, Southern; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D020868:Gene Silencing; D017930:Genes, Reporter; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D006358:Hot Temperature; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D016376:Oligonucleotides, Antisense / Q000737:chemistry / Q000494:pharmacology; D010641:Phenotype; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D034741:RNA, Small Interfering; D022661:RNA, Untranslated / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D014158:Transcription, Genetic; D019076:Transgenes
D004268:DNA-Binding Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D016376:Oligonucleotides, Antisense; D010940:Plant Proteins; D034741:RNA, Small Interfering; D022661:RNA, Untranslated; D014157:Transcription Factors; D012313:RNA; D008156:Luciferases