Mechanisms Of OsNDPK1 Improving Disease-resistance And Promoting Cell Division Of Plant

Brassinosteroids (BRs) are plant hormones that they have very strong physiological activity and play important roles in plant growth and development, such as promoting cell elongation and division, improving disease-resistance of plant. Identifying the BR regulated components which regulating the above growth process is the base to elucidate the regulating mechanism of BR in plant growth and development. In our early study, we identified some BR-regulated proteins using two-dimensional polyacrylamide gel electrophoresis. One of them is Nucleoside Diphosphate Kinase1 ( OsNDPK1 ) after analysis by mass spectrometry, OsNDPK1 is regulated by BR,the level of OsNDPK1 was elevated after treated with BR in wide type rice and inhibited in BR-deficient mutant brd1-3. These results showed that OsNDPK1 was up-regulated by BR, suggesting the expression level of OsNDPK1 was induced in rice after inoculating with Xanthomonas oryzae pv.oryzae (Xoo). These implied that OsNDPK1 might work in improving plant resistance.In this study, we analyzed the function of OsNDPK1-OE in disease-resistance through analyzing the phenotype of gaining-function transgenic Arabidopsis. The results are as follows:1. OsNDPK1 is involved in the regulation of plant disease resistance. (1) The ability of disease-resistance to plant pathogenic fungi- Botrytis cinerea (BC22) and pathogenic bacteria Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) was enhanced in over expression OsNDPK1 transgenic Arabidopsis thaliana enhance. (2) The expression level of the key disease-resistance gene PR1, NPR1 in OsNDPK1-OE were higher than that in Col-0 obviously. It was indicated that OsNDPK1 could induce the expression of PR1 and NPR1 to enhance disease-resistance of plant. (3) The content of SA in OsNDPK1-OE was higher than Col-0 Arabidopsis thaliana obviously after inoculating with Botrytis cinerea (BC22), suggesting OsNDPK1 activating the defense pathway which induced by SA. (4) The expression level of PAD4 and EDS1 which could promote SA accumulation were induced in OsNDPK1-OE obviously after inoculating with Botrytis cinerea (BC22). (5) The content of dissolved carbohydrate in OsNDPK1-OE was higher than that in Col-0 Arabidopsis obviously after 48 h inoculating with Botrytis cinerea (BC22), which indicated that OsNDPK1 could promote the content of dissolved carbohydrate to enhance disease-resistance of plant. (6) The expression of gene Cha1 which code the chitinase maintained high level for longer time in OsNDPK1-OE than in Col-0 Arabidopsis thaliana after inoculating with Botrytis cinerea (BC22) for 0、1、3、6、12、24 hours, the results indicated that the ability to degradate the fungus cell wall’s chitin of the plants of OsNDPK1-OE could maintain for longer time, so enhanced the disease-resistance of Arabidopsis thaliana to fungus. (7) The callose in the OsNDPK1-OE’s leaf were much more than Col-0 Arabidopsis thaliana’s leaf, and the content of callose increased follow the time after inoculating with pathogenic bacteria Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), suggesting OsNDPK1-OE resisting the infection of Pst DC3000 via inducing callose’s accumulation.2. OsNDPK1 regulated the pathway of BR signal transduction positively. The expression level of both the BR inducing factor Saur-AC1 and the transfer factor BZR1 and BES1 in BR signal transduction are all increased in OsNDPK1-OE, these suggested that OsNDPK1 regulated the BR signal transduction positively.3. OsNDPK1 is involved in the regulation of cell division. (1) The length of hypocotyl in OsNDPK1-OE was longer than Col-0 Arabidopsis thaliana. (2) The number of hypocotyl cell in OsNDPK1-OE was more than Col-0 Arabidopsis thaliana. (3) The expression level of CycD2、CDC2 which could shorten cell division cycle in OsNDPK1-OE was higher than that in Col-0 Arabidopsis thaliana.From above results, OsNDPK1 was up-regulated by BR and could enhance the ability of disease-resistance of plant; In addition, OsNDPK1 could promote the progress of cell division. OsNDPK1 regulated the path way of BR signal transduction positively. These results opened up a new research approach for researching the mechanism of BR how to enhance the disease-resistance of plant and promote cell division.