HO-1 GENE EXPRESION IS NOT EPIGENETICALLY RESTRICTED AND INVOLVES STRESS-RELATED TRANSCRIPTION FACTOR

SANTA CRUZ, DM; YANNARELLI G.; PACIENZA, N; ZILLI, CG; TOMARO, M.L; BALESTRASSE, KB

Congreso; 49 Reunion SAIB; 2013

Hemo oxygenase-1 (HO-1) plays a protective role against oxidativestress in plants. The mechanisms regulating its expression, however,remain unclear. Here we studied the methylation state of a GC richHO-1 promoter region and the expression of several environmentalstress associated-transcription factors (TFs) in soybean plantssubjected to ultraviolet-B (UV-B) radiation. Genomic DNA andtotal RNA were isolated from leaves of plants irradiated with 7.5and 15 kJ.m-2 UV-B. A 304 bp HO-1 promoter region was amplifiedby PCR from sodium bisulfite-treated DNA, cloned into pGEM-Tplasmid vector and evaluated by DNA sequencing. Bisulfitesequencing analysis showed similar HO-1 promoter methylationlevels in control and UV-B-treated plants (C: 3.0±0.6%; 7.5:3.14±0.5%; 15: 2.9±0.5%). Interestingly, HO-1 promoter wasstrongly unmethylated in control plants. Quantitative RT-PCR ofTFs showed that GmMYB177, GmMYBJ6 and GmWRKY21 butnot GmWRK13 were induced by UV-B irradiation, inferring thatthe former group mediates HO-1 up-regulation. These resultsindicate that HO-1 gene expression is not epigenetically regulated.Moreover, the low level of HO-1 promoter methylation suggeststhat this antioxidant enzyme can rapidly respond to environmentalstress. Finally, this study has identified some stress-related TFsinvolved in HO-1 up-regulation under UV-B radiation.