Functional Analysis Of NCP1, An Interactor Of Maize Transcription Factor ABP9, In Plant Responses To Abiotic Stress

Oxidative stress is the common mechanism by which abiotic stresses affect plant growth and development. Plant has evolved series enzymatic and non-enzymatic antioxidant systems to defend the oxidative stress. Researching on the signal transduction pathway of anti-oxidant menchanism and stress response system have a great guiding meaning in improving crop anti-stress breeding.Our previous studies have cloned a bZIP transcription factor ABP9 binding to cis-element ABRE2 of Cat1 gene from maize embryo cDNA library using yeast one hybrid system,and the ABP9 transgenic Arabidopsis and maize have the abio-stress resistance ability. However,little was known about how ABP9 protein was regulated in abiotic stress, for that series proteins interaction with ABP9 have been cloned,and NCP1(ABP Nine Complex Protein 1,NCP1)was one of the function unknown protein.The objective of the study is to investigate the function of NCP1 and the interaction between NCP1 and ABP9 using transgenic Arabidopsis, and then get a good understanding of the components and mechanism of ABP9 in respond to stress signaling. The main results obtained are as follows:1. Under virous abiotic stress such as salt,ABA,PEG6000,cold and H2O2,the expression profile of NCP1 and ABP9 have similar trend.2. Construct a transformation vector of pCHF3-NCP1,and NCP1 transgenic Arabidopsis plants were obtained through agro-bacterium mediated transformation via flower infection technology. Stress tolerance assays of NCP1 transgenic Arabidopsis plants showed that NCP1 was an abiotic stress sensitive gene,and has the ability to up-regulated the ROS level.3. Constitutive expression of NCP1 in Arabidopsis resulted in enhanced ABA sensitivity in seed germination and root elongation, and insensitivity in stomatal aperature.4. Cross the NCP1 transgenic Arabidopsis plants with ABP9 transgenic Arabidopsis plants.Two double over-expression lines were obtained.5. NCP1 and ABP9 overexpression in Arabidopsis enhanced ABA sensitivity in seed germination , root elongation and stomatal closure,but resulted in insensitivity in seedling growth.6. Drought and salt tolerance assays showed that double over-expression lines have a strong tolerance ability than wild type,but a weak tolerance ability than ABP9 transgenic Arabidopsis line. It's means that the interaction between NCP1 and ABP9 could regulate the stress resistant ability of plant.7. ROS staining assays showed that double over-expression lines still have the ability of scavenging ROS under both normal growth condition and salt condition. 8. Flowering assays showed that both NCP1 transgenic lines and double over-expression lines flowered earlier than wild type Arabidopsis under salinity condition. But the ABP9 transgenic Arabidopsis line delayed the nomal development and flowering.9. Real-time quantitative PCR analysis revealed that a large body of stress responsive genes including those for stress defence,ABA signaling and ROS scavenging were down-regulated in NCP1 transgenic plants.In summary,the results demonstrate that NCP1 interact with ABP9 , and then play a significant role in regulating the ABA/stress response, ROS levels, gene expression and flowering. All of the researches have layed a good basis for further investigate the ABP9 stress signal transduction pathway.