The Mechanism Of BHLH Transcription Factor-coding Gene RHD In Response To Aluminum Stress In Arabidopsis

A1 maybe is the most widespread metal in the earth,in acid soils,namely pH<5,the toxic Al3+ ion becomes increasingly soluble and to be a significant constraint factor about crop productivity.Acid soils are widespread,especially in the subtropics and tropics,and the plant root apex is the major target of Al toxicity,in Arabidopsis,the root-apex transition zone(TZ),located between the root meristem and the elongation area,is the most sensitive part to Al.Al is rapidly accumulated in the roots,and the main binding site of Al3+ in the root is the apoplast,in the apoplast,the primary binding site is probably the pectic matrix,because pectin has negatively charged carboxylic groups,which has a high affinity for Al3+.Cell elongation demands cell turgor pressure driving expansion,and the pectin may control the cell wall malleability.It has been known that,plant which is treated with Al will reduce cell wall extensibility.RHD is a transcription factors,belonging to the family of bHLH,involving in root hair initiation,the change of cell wall is the result of root hair initiate.Hence,the alteration of the initiation of root hair would result in a series of abnormal biological processes.The Al content in the rhd mutant is higher compared with wild type,but there is no difference of the Al content in the apoplast,maybe the phenotype has no relationship with the apoplast.The experiment of Hematoxylin staining,Morin staining,the results all discovered that the aluminum content in the mutant is higher than wild type,also in the transition zone.But the qRT-PCR show that,the genes related to aluminum tolerance,such as STOP1,ALMT1 MATE,ALS3 all remain invariant,that is to say,the phenotype of the mutant,have no relationship with these genes.RNA sequence finds that the changed genes,for the most case,related to the cell wall.It may suppose that,the changed of the cell wall structure is probably the reason of root hair defective mutant sensitive to aluminum.My paper found that,cell wall participated in the aluminum tolerance passway,but there are still a series of experiments need to do.