Abstract
Rubber trees (Hevea brasiliensis) are susceptible to low temperature and therefore are only planted in the tropical regions. In the past few decades, although rubber trees have been successfully planted in the northern margin of tropical area in China, they suffered from cold injury during the winter. To understand the physiological response under cold stress, we isolated a C-repeat binding factor 1 (CBF1) gene from the rubber tree. This gene (HbCBF1) was found to respond to cold stress but not drought or ABA stress. The corresponding HbCBF1 protein showed CRT/DRE binding activity in gel shift experiment. To further characterize its molecular function, the HbCBF1 gene was overexpressed in Arabidopsis. The HbCBF1 over expression (OE) line showed enhanced cold resistance and relatively slow dehydration, and the expression of Arabidopsis CBF pathway downstream target genes, e.g. AtCOR15a and AtRD29a, were significantly activated under non-acclimation condition. These data suggest HbCBF1 gene is a functional member of the CBF gene family, and may play important regulation function in rubber tree.
Highlights
Temperature determines the geographic distribution of plants in the world
Plants in the temperate regions have the ability to enhance their freezing tolerance by a process called cold acclimation, during which the plants adjust their metabolism to cold temperature and acquire enhanced freezing tolerance after being exposed to nonfreezing cold temperatures [1]
Due to the cold susceptible trait, rubber trees were traditionally planted in a restricted region between 15° north and 15° south latitudes
Summary
Temperature determines the geographic distribution of plants in the world. Plants in the temperate regions have the ability to enhance their freezing tolerance by a process called cold acclimation, during which the plants adjust their metabolism to cold temperature and acquire enhanced freezing tolerance after being exposed to nonfreezing cold temperatures [1]. Two types of cold acclimation pathways are found in plants: ABA dependent. ABA dependent pathway requires the accumulation of ABA and the activation of several transcription factors, such as ABFs [16,17], MYBs and MYCs [18,19]. The transcription factors bind with ABRE, MYBRS, and MYVRS cis-elements, and activate functional genes, such as RD22 and RD29B. The most intensively studied ABA independent pathway is ICE1-CBF regulon, in which the ICE1 (INDUCER OF CBF EXPRESSION1) proteins is activated by secondary signal during cold stress. The activated ICE1 induces the expression of CBF transcription factors [10,20,21], which bind with CRT/DRE motif [22,23] and regulate the expression of COR genes that confer freeze tolerance. Until now CBF and its homologs have been cloned in more than fifty plant species[24], such as Arabidopsis, maize, grape, eucalyptus, citrus, wheat, barley, and tomato [24,25,26,27,28,29,30] et al
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