Study Of IAA And MAPKs Response Mechanism To Malic Acid Efflux Signal Transduction Pathway In Wheat Under Aluminum Stress

Aluminum toxicity is one of limiting factors in acid soil. It is of great importance to study the Al resistant mechanism for solving crop aluminum toxicity in acid soil, increasing crop yields and cultivating Al-resistance crop varieties. We mainly used two wheat(Triticum aestivum L.) cultivars ET8 and ES8 differing in Al resistance for our study. Relationship of Al-induced malic acid efflux and MAPKs cascade pathway was revealed by the effect of IAA and protein kinase inhibitor to Al-induced malic acid efflux, Relationship of Al toxicity and auxin signal transduction system was revealed by the effect of IAA and protein kinase inhibitor PAO to ARF2 and expressions of root apex cells exposure to Al(50μmol·L-1).Relationship of Al toxicity,IAA and MAPKs cascade pathway was revealed by the response of MAPK12 and MAPK14 expressions to Al toxicity and IAA.The main resuits were as follows: 1. Effect of protein kinase inhibitor and IAA to Al-induced malic efflux in ET8 and ES8 differing in Al tolerance exposure to Al(50 μmol·L-1)Compared with CK, protein kinase inhibitor PAO, CHX treatment alone did not affect the efflux of malic acid from 4-day-old seedlings. Compared with Al(50 μmol·L-1), PAO(CHX) co-treatment with Al(50 μmol·L-1) could significantly inhibit the efflux of malic acid,and the inhibition elevated with the increasing PAO(CHX) concentration. Compared with Al(50 μmol·L-1) and PAO(5, 10 μmol·L-1) co-treatment, Al, PAO cotreatment with IAA could significantly enhance the efflux of malic acid. All of the above proved that IAA was involved in regulating Al-induced malic acid efflux in wheat. And preliminary showed that MAPKs cascade pathways may be involved in malic acid secretion.2. Effect of protein kinase inhibitor PAO and IAA to ARF2 and IAA protein expressionsin ET8 and ES8 differing in Al tolerance exposure to Al(50 μmol·L-1)1) Different concentration of aluminum(0, 25, 50, 100 μmol·L-1) treatment showed that Al could promote ARF2 expression in root apex of ET8, and inhibit ARF2 expression in ES8; And it also could inhibit IAA Protein expression in ET8 and ES8. 2) No matter how Al or not, IAA(50 μmol·L-1)treatment could inhibit the expression of ARF2 and IAA protein in wheat. 3) Compared with Al(50 μmol·L-1), Al and PAO(5,10 μmol·L-1) cotreatment could significantly inhibit the expression of ARF2 and IAA protein in wheat, showed that PAO could inhibit the expression of ARF2 and IAA protein in wheat under Al stress. And the inhibition elevated with the increasing PAO. 4) Compared with Al(50 μmol·L-1) and PAO(5, 10 μmol·L-1) co-treatment, Al, PAO co-treatment with IAA could significantly inhibit the expression of ARF2 and IAA protein in wheat. 3. Response of and MAPK14 in root apex cells of ET8 and ES8 to PAO and IAA under Al stress1) Different concentration of aluminum(0, 50, 100 μmol·L-1) treatment showed that Al could inhibit the expression of MAPK12 in wheat, and enhance the expression of MAPK12 in wheat. Then time-dose treatment showed that the expression of MAPK12 could decreasing with the extension of processing, while MAPK14 expression increasing. The results indicated that the expression of MAPK12 was inhibited with dose and timedependent by Al treatment, while the expression of MAPK14 was activated with dose and time-dependent by Al treatment. 2) Compared with CK, IAA treatment alone could significantly inhibit the expression of MAPK12, and enhance the expression of MAPK14. Compared with Al treatment, IAA and Al co-treatment showed stronger inhibition on MAPK12 expression, and no work on MAPK14 expression. 3) PAO(5, 10 μmol·L-1) could significantly enhance the expression of MAPK12 under Al stress, and the low concentration(5 μmol·L-1) showed stronger promotion than the high concentration(10 μmol·L-1). While PAO(5, 10 μmol·L-1) could significantly inhibit the expression of MAPK14 under Al stress, and the higher concentration(10 μmol·L-1) showed stronger inhibition. 4) Compared with Al(50 μmol·L-1) and PAO(5, 10 μmol·L-1) co-treatment,Al,PAO co-treatment with IAA could significantly inhibit the expression of MAPK12 and MAPK14 in wheat. It showed that MAPK12 and MAPK14 could response to IAA.Al treatment could induce malic acid efflux and series of physiological reactions to confrontate aluminum stress by activating auxin signal transduction pathway and MAPKs cascade pathway.