A study on the mode of action of thermospermine in the stem growth of plants

热精胺在植物中起抑制木质部分化的作用，缺乏热精胺会导致木质部导管过度增生和严重的侏儒症。为了了解热精胺的作用模式，我们分离了一个需要热精胺的拟南芥突变体的抑制突变体，发现sac53-d和sac56-d突变体分别在编码核糖体蛋白RACK1和L4的基因上存在缺陷。我们进一步发现热精胺在功能上可以被去精胺取代。化学筛选实验表明，热精胺和生长素在木质部分化中具有相反的作用。

Thermospermine functions in repressing xylem differentiation in plants and its deficiency results in excess proliferation of xylem vessels and severe dwarfism. To know the mode of action of thermospermine, we have isolated suppressor mutants of a thermospermine-requiring mutant of Arabidopsis that restore the dwarf phenotype, and revealed that sac53-d and sac56-d mutants are defective in a gene encoding ribosomal protein RACK1 and L4, respectively. We further found that thermospermine can be functionally replaced with norspermine. A chemical screening experiment revealed that thermospermine and auxin have an opposite function in xylem differentiation.