IDENTIFICATION OF GENES UP-REGULATED IN RESPONSE TO LEAD EXPOSURE IN SUNFLOWER (Helianthus annuus L.)

In this study, Differential display reverse transcription (DDRT) technique was used to analyze differentially upregulated genes in Helianthus annuus in response to Pb exposure. Seeds of sunflower were germinated in lead contaminated soils and untreated plants were used as control. Twenty differentially expressed fragments were identified and characterized. The fragments were classified according to their expression levels. The significance of the function of the identified differentially expressed genes was discussed in relation to their possible roles as stress genes. Two fragments showed no significant homology with any database sequences in the GenBank. Results of the database sequence alignment identified two fragments showed homology to unclassified and unknown genes; two cDNA fragments show homology with salinity responsive genes, three fragments showed homology with drought responsive genes, one fragment showed homology with cold responsive gene, one fragment showed homology with oxidative responsive gene and one fragment showed homology with biotic stress resistance gene. More importantly, a fragment had significant homology with EST of Glycine max similar to serine/threonine-protein kinase gene, a fragment showed significant homology with EST of Arabidopsis thaliana putative anion transporter 2 (ANTR2) mRNA, a fragment had significant homology with EST of Helianthus annuus delta-12 oleate desaturase (FAD2- 2) gene, a fragment showed significant homology with EST of Dianthus caryophyllus putative MtN3-like protein mRNA, two fragments showed significant homology with EST for NADH dehydrogenase chain 3 (nad3) genes, a fragment had significant homology with EST from Volvox sp. similar to cytochrome oxidase subunit 1(CoxI) and a fragment showed significant homology with EST23 of Medicago truncatula MLP-like protein. These results implicate that several pathways are involved in the plant's response to Pb exposure which still needs to be elucidated further.