Isolation And Functional Characterization Of DREB Transcription Factor And Genes Involved In Lignin Biosynthetic Pathway From Broussonetia Papyrifera L.

Common papermulberry (Broussonetia papyrifera L.), classified as moroideae, is a light-loving deciduous arbor and an endemic production forest in China. It is distributed among most region of China and adapts well to various environmental stresses, such as good tolerances to drought and leanness, and growing in acid soil. In particular, it has been considered as an important paper pulp resource owing to its fibre with high quality and growing fast. In this paper, a DREB-like gene and two genes involved in lignin biosynthetic pathway were isolated by RACE methods from Broussonetia papyrifera, and their sequence characters, expression patterns and functions were deeply analyzed to understand clearly molecular mechanism of plant response to various abiotic stresses and of lignin biosynthesis. The main results are follows:1. A cDNA clone encoding DRE-binding protein, designated BpDREB, was isolated from a woody plant, Broussonetia papyrifera. BpDREB protein has three characteristic domains of the transcription factor, namely an AP2/EREBP domain, a nuclear localization signal and an acidic activation domain. The deduced amino acid sequences of BpDREB showed no significant sequence similarity with those of other known DREBs except for the conserved AP2/EREBP DNA-binding domain. DNA gel blot analysis indicated BpDREB is a one-copy gene. The expression of the BpDREB gene was induced by dehydration and high-salt conditions. No significant changes in the BpDREB expression were observed under ABA or low-temperature treatments.2. The BpDREB protein specifically bound to the DRE sequence and activated the transcription of two report genes HIS3 and LacZ driven by the DRE sequence in yeast strain JM4271. When fused to the LexA DNA-binding domain, BpDREB could function as a transactivator in yeast strain EGY48. These results testified that BpDREB contained a DNA-Binding domain and an acidic activation domain.3. We transformed the BpDREB gene into Arabidopsis with Agrobacterium EHA105 containing expression vector of p3301-121-BpDREB by floral dip method.