Abstract: 【Objective】AP2/ERF transcription factors play important roles in response to abiotic stress in plant. The objectives of this study are to clone ERF genes related to abiotic stress in rubber tree, analyze their expression patterns in response to abiotic stress and identify their biological functions by overexpressing in Arabidopsis thaliana so that it can provide candidate genes for rubber breeding in relation to stress tolerance. 【Method】The full cDNA sequence of HbERF1 was cloned from the rubber tree by RACE technology, then the temporal and spatial expression patterns of this gene were investigated under abiotic stress by real-time PCR. The HbERF1-overexpressing Arabidopsis was established by Agrobacterium-mediated transformation. The overexpressing lines were identified by Southern blotting and qRT-PCR. The phenotype and gene expression were analyzed under drought, NaCl and PEG stress in overexpressing lines, and the functions of HbERF1 were characterized preliminarily. 【Result】 HbERF1 (GenBank No. JQ914647) had no intron. The full-length cDNA of HbERF1 was 1 178bp in length, containing a 642-bp open reading frame flanked by a 62-bp 5’-UTR and a 474-bp 3’-UTR. HbERF1 encoded a 213 aa protein, which contained one AP2 domain and one EAR motif. The results of phylogenetic analysis showed that HbERF1 protein was classed into B-1 subgroup of ERF subfamily, and it showed 72%, 62%, and 61% identity with RcERF, PtERF46 and AtERF4, respectively. The real-time PCR analysis showed that HbERF1 was NaCl-, PEG- and drought -responsive in the leaves and bark of rubber tree. The expression of HbERF1 was repressed by abscisic acid (ABA) and methyl jasmonate (MeJA) in leaves and bark, meanwhile also by salicylic acid (SA) in the bark. Under NaCl- and PEG stress, HbERF1 was down-regulated in the first stress phase (≤8 h) in leaves, while HbERF1 was strongly induced in bark when it was stressed for 4h. Under drought stress, the expression of HbERF1 continuously increased in leaves and bark with the increase of drought degree, and the expression was higher in bark than in leaves. The overexpression of HbERF1 enhanced the tolerance to NaCl, PEG and drought in Arabidopsis. The expression of ethylene receptor gene, AtETR1 and AtERS1, were also repressed by HbERF1 overexpression in Arabidopsis, in which the expression of AtETR1 and AtERS1 was about 19-fold and 9-fold lower than those in the control, respectively, and the difference was highly significant(P＜0.01). Under NaCl stress, the expression of AtRD22 and AtRD29A had a 115-fold and 100-fold increase in overexpressing Arabidopsis, respectively, and these two genes were also induced under 20% PEG stress. Nearly all of the leaves became dehydrated and wilted in wild-type Arabidopsis after it was watered with 300 mmol•L-1NaCl for 15 days, while only few leaves became dehydrated and wilted in overexpressing line S1. Line S1 had been in the reproductive growth since it was watered with 20% PEG for 15days, while wild-type Arabidopsis was still in the vegetative growth, and some leaves became dehydrated. After stopping watering for 2 weeks, wild-type Arabidopsis was more wilted than line S1; and the survival rate of wild-type and overexpressing Arabidopsis was 35.0% and 95.0% after re-watered for 1 week, respectively. 【Conclusion】 HbERF1 was induced by ABA, MeJA, SA and ethylene (ETH), and it is a positive regulator of ETH-responsive genes and drought tolerance in the rubber tree.

Key words: Hevea brasiliensis , transcription factor , abiotic stress , ERF