Function Analysis Of At STOP1’s Interacting Protein, NaKR1 Under Aluminum Stress In Arabidopsis

Aluminum is the most abundant metal elements in the earth. In general, aluminum is present with the form of solid in the soil, when the p H≤5, it dissolves into soil solution, which results in the ion toxicity. Acid soil stress and aluminum toxicity are the major limit factor of crop production now.Plant has evolved a serious of aluminum tolerance mechanisms during the long-term adaptation. STOP1(Sensitive to proton rhizotoxicity 1) is an important transcription factor about aluminum tolerance in Arabidopsis, which has 4 C2H2 zinc finger domains. STOP1 regulates transcription of multiple genes critical for tolerance and low p H, and the mutant has an Al-sensitive phenotype. In our previous work, we had found the interaction protein of STOP1—Na KR1(Sodium Potassium Root Defective1), by yeast two-hybrid screening. Na KR1 encoding a soluble protein consist of 319 amino acids, which have a HMA domain in the C terminal. It specific expresses in phloem companion cells of Arabidopsis.To further verify the interaction domain of Na KR1 and STOP1, we divided the genes to C terminal and N terminal via their function domain. We also get Na KR1 overexpressing Arabidopsis lines with a 3×HA-LUC tag for subsequent experiments. The transcript expression levels of aluminum tolerance related genes were detected, such as At ALMT1、At MATE、At ALS3 etc. The results are showed as below:1. The interaction domain of Na KR1 and STOP1 are both N-terminal. It means that Na KR1 N-terminal interacting with STOP1 N-terminal, and Na KR1 has no selfactivated. It has nothing to do with the functional domain.2. Na KR1 overexpressing Arabidopsis lines do not respond to low p H, but show Al-sensitive characteristics, such as root length is inhibited at 2-3 days after germination under aluminum treatment. With time goes, the root inhibition eased. Comparing with wild type Arabidopsis, Na KR1 overexpression root is shorter, deeper apical staining, suggesting aluminum accumulation in Na KR1 overexpression Arabidopsis roots may be one reason of aluminum sensitive.3. The transcript expression level of ALMT1 in wild-type Arabidopsis decreased gradually after the peak value at 12 h while in Na KR1 over expressing Arabidopsis remains at a high and stable level, illustrating the Aluminum toxicity has not eased;4. The transcript expression level of STOP1 increases after 12 h aluminum treatment in Na KR1 over expressing Arabidopsis. The aluminum tolerance related genes regulated by STOP1 such as ALS1, ALS3, STAR1 are also increased in the same trend with STOP1. Al-sensitive of Na KR1 overexpressing Arabidopsis may be associated with cell wall functional regulation.5. The transcript expression level of FRD3 and WRKY46 has little difference between wild type and Na KR1 overexpression Arabidopsis, speculating Al-sensitive of Na KR1 overexpressing has noting to do with the aluminum transportation to the shoot, neither other transcription inhibitors.