45F-15 |
Heat-shock genes are induced by storage at low temperature in mango fruit mesocarp |
D. M. LEON-GUTIERREZ1, J. De la Cruz1, H. S. Garcia1, and M. A. Gomez-Lim2. (1) UNIDA, Instituto Tecnologico de Veracruz, M.A. de Quevedo # 2779, Col. Formando Hogar, Veracruz, Ver., 91897, Mexico, (2) CINVESTAV-Irapuato, Apdo. Postal 629, Irapuato, Gto., 36500, Mexico We have found that heat shock (HS) treatment before refrigeration of mango fruit can reduce the severity of chilling injury (CI) symptoms. It has been reported that after HS several genes in plant cells are induced, new mRNAs are transcribed and new heat shock proteins (HSP) are synthesized. HSP have been correlated with increased thermotolerance and protection of plant cells against low temperature stress. The objective of this work was to identify HSP genes and evaluate if any changes in gene transcription (new mRNAs) were induced in mango after HS. Fully-ripened Manila mangoes and young mango leaves were harvested, sorted, washed and divided into lots. Fruits were placed directly at 6 ºC or heated at 38 ºC for 36 h before storage at 6 ºC for 20 days. DNA was extracted from leaves using the CTAB method and then used for amplification of HSP genes by PCR using primers derived from consensus regions from HSP. PCR products were sequenced using a DNA sequencer. PCR amplification of HS mango genes and sequencing of these products originated nucleic acid sequences of 523, 273 and 324 base pairs. Comparison of the sequences with published sequences in the genbank revealed that the 324 bp fragment shared considerable homology with HSP70 genes from rice (Oryza sativa), sorghum and fruit fly (Drosophila melanogaster). Northern Blot analysis was performed using RNA extracted from control and heat-treated mango fruit mesocarp, hybridized with the PCR fragment. HSP70 transcripts were detected in refrigerated and preheated fruit and the levels of the mRNAS were constant during the 20 days of low temperature storage. These HSP gene sequences are the first reported for a tropical fruit such as mango. The induction of the transcripts suggest an important role of HSP 70 in protecting and recovery mechanism of cells during and after chilling and heat stress.
Session 45F, Fruit & Vegetable Products: Fruits (Fresh)
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