植物在受伤时表现出惊人的调节器官再生的能力。叶外植体的切除促进吲哚-3-乙酸(IAA)的生物合成,极性运输到切除区域,其中细胞命运转变导致根建立细胞的规范,以诱导从头根再生。植物的再生能力已被用于开发体外组织培养技术。这里,我们报告说,在富含2,4-二氯苯氧基乙酸(2,4-D)的愈伤组织诱导培养基(CIM)上,叶片外植体受伤部位附近的IAA积累对于诱导愈伤组织至关重要。值得注意的是,高浓度的合成生长素,2,4-D,由于其有限的外排,不能补偿IAA的作用;相反,它在体外组织培养的早期阶段通过负反馈机制降低IAA的生物合成,延迟愈伤组织的启动。CIM培养的叶片外植体中的生长素负反馈回路是由生长素诱导型AP2转录因子介导的,射孔再生增强器2(ESR2),及其相互作用的伴侣组蛋白脱乙酰酶6(HDA6)。ESR2-HDA6复合物直接结合,并删除H3ac标记,YUCCA1(YUC1),YUC7和YUC9位点,因此抑制生长素的生物合成并抑制2,4-D-richCIM的细胞命运转变。这些发现表明,ESR2和HDA6对生长素生物合成的负反馈调节会干扰适当的细胞命运转变和愈伤组织的启动。
Plants exhibit an astonishing ability to regulate organ regeneration upon wounding. Excision of leaf explants promotes the biosynthesis of indole-3-acetic acid (IAA), which is polar-transported to excised regions, where cell fate transition leads to root founder cell specification to induce de novo root regeneration. The regeneration capacity of plants has been utilized to develop in vitro tissue culture technologies. Here, we report that IAA accumulation near the wounded site of leaf explants is essential for callus formation on 2,4-dichlorophenoxyacetic acid (2,4-D)-rich callus-inducing medium (CIM). Notably, a high concentration of 2,4-D does not compensate for the action of IAA because of its limited efflux; rather, it lowers IAA biosynthesis via a negative feedback mechanism at an early stage of in vitro tissue culture, delaying callus initiation. The auxin negative feedback loop in CIM-cultured leaf explants is mediated by an auxin-inducible APETALA2 transcription factor, ENHANCER OF SHOOT REGENERATION 2 (ESR2), along with its interacting partner HISTONE DEACETYLASE 6 (
HDA6). The ESR2-
HDA6 complex binds directly to, and removes the H3ac mark from, the YUCCA1 (YUC1), YUC7, and YUC9 loci, consequently repressing auxin biosynthesis and inhibiting cell fate transition on 2,4-D-rich CIM. These findings indicate that negative feedback regulation of auxin biosynthesis by ESR2 and
HDA6 interferes with proper cell fate transition and callus initiation.