Preliminary Identification Of U-Box Protein PUB53 From Arabidopsis Thaliana

The ubiquitination pathway is involved in the regulation of plant growth, development and stress response. U-box proteins play important roles in plant ubiquitination pathway as ubiquitin ligases. Recent studies have showed that Arabidopsis ARM/U-box proteins are important regulators of growth, development and response to environmental stress. However, the functions of a class of U-box protein including AtPUB53 with kinase domains are still unclear.We have cloned the full-length DNA sequence of Arabidopsis U-box protein AtPUB53 and its upstream promoter sequence. After systematic analysis of AtPUB53 promoter cis-elements and chip expression profiles, we found the spatial and temporal expression pattern, light and abiotic stress response mode of AtPUB53. AtPUB53 shows tissue-specific expression pattern, high expression abundance in roots and seeds while low abundance in the rosette leaves. Expression of AtPUB53 was upregulated in the process of seed germination and reproductive growth, however, downregulated was found in the leaf senescence process. In the process of far-red light and blue light reversing flowering promotion effect of red light, the AtPUB53 expression is upregulated, whereas AtPUB53 expression was downregulated by salt, drought, heat and cold stresses.For function identification of AtPUB53 in Arabidopsis growth, development and response to abiotic stress, we constructed the 35S::AtPUB53 over-expression and ProAtPUB53::GUS vectors. Furthermore, two T-DNA insertional mutants pub53-1 and pub53-2 were screened and identified. It was shown that pub53 flowered earlier than Col-0 under the long day photoperiod. Meanwhile, pub53 showed hypersensitivity to salt stress. Seed germination rate, seedling cotyledon green rate and biomass accumulation significantly decreased under salt stress, meanwhile, primary root length was significantly shorter than Col-0 under salt stress. Under the osmotic stress caused by mannitol, pub53 showed similar sensitivity phenotype. Under drought stress, pub53 showed enhanced drought tolerance. In addition, pub53 was slight sensitive to ABA stress.The above results demonstrate that the PUB53 is involved in many physiological processes including flowering and abiotic stress responses, indicating the cross-talk between plant development and abiotic stress signaling, and important functions of ubiquitination pathway in regulating plant signaling transduction.