| The cell wall-associated kinases(WAKs),which represent a unique receptor-like kinases(RLKs)subfamily in plants,consist of an extracellular domain,a transmembrane domain and a cytoplasmic serine(Ser)/threonine(Thr)protein kinase domain.The extracellular domain which is covalently associated with cell wall through pectin can sense changes from the cell wall,while intracellular kinase domain can pass way the signal via phosphorylating.WAKs are excellent candidates signaling molecules that directly link and allow communication between the cell wall and cytoplasm,and then,the plants product a series of physiological and biochemical responses.In the present study,the wild type(Oryza sativa cv Nipponbare)and two lines OsAK11 silencing by RNA interference,oswak11-1 and oswakll-2 were investigated under several concentrations of copper.We have measured the effects of OsWAK11 mutation on plants growth and Cu accumulation,and also have analyzed uronic acid of cell wall components,their Cu-binding ability and esterification of cell wall in wild type,oswakll-1 and oswakll-2.Moreover,the expressions of four genes including pectin esterase gene OsPME14,two mitogen activated protein kinase OsMPK4,OsMPK14 and a metallothionein gene OsMT2c have been examined using quantitative RT-PCR.The results showed that the OsWAK11 inhibited results in more sensitive to copper compared with wild type.The growth of oswak11-1 oswak11-2 are shorter than wild type in the whole growth cycle because of the dwarf forth leaf.We observed the cell elongation of oswak11-1 and oswak11-2 is more inhibited than that of wild type,and it’s the main reason about the dwarfism through the paraffin sections.At the same time,we also found that oswak11-1 and oswak11-2 seedlings become more sensitive to Cu-induced oxidative stress,then the oxidative damage disturbed the integrity of plasma membrane.The mutation of OsWAK11 led to changes of uronic acid contents of cell wall components in roots and shoots when exposed to excessive Cu,and promote the esterification of cell wall by decreasing the expression of pectin esterase OsPME14,subsequently inhibit Cu-binging ability of cell wall.So,the weakness of efflux effect of cell wall make the intracellular metal Cu still more.The expression of OsMPK4 and OsMPK14 geneswas downregulated in oswak11-1 and oswak11-2 plants by qRT-PCR,while there was no obvious significance of OsMT2c expression in wild type,oswakll-1 and oswakll-2.In summary,these data indicate that the mutation of OsWAKll inhibited the cell elongation in root and leaf of two mutant lines,and then lead to plant dwarfism,the components of the cell wall were changed and lead to the decreasing Cu-binding ability of cell wall in oswak11-1 and oswakll-2,and the mutation of OsWAKll aggravate Cu-induced oxidative stress in roots of oswak11-1 and oswak11-2. |
