Secreted CLAVATA3/EMBRYO SURROUNDING REGION (CLE) peptide ligands dimension the stem cell niche of Arabidopsis shoot meristems by signalling through redundant and cross-compensating CLAVATA1 (CLV1)-type receptor kinases. In the root meristem, the CLV1 homologues BARELY ANY MERISTEM 1 (BAM1) and BAM2 drive CLE13/16-mediated formative divisions that produce the ground tissue layers. Here we report that BAM1/2 are also required to initiate the vascular phloem lineage and that cross-compensation between CLV1-type receptors as observed in the shoot does not operate similarly in the root. Rather, we find that BAM3-mediated CLE45 signalling antagonizes BAM1/2-mediated CLE11/12/13 signalling in the phloem initials but not in the ground tissue. We further observe spatiotemporally contrasting CLE signalling requirements for phloem initiation and differentiation, which are shaped by the SHORT ROOT (SHR) pathway. Our findings thus suggest an intricate quantitative interplay between distinct and antagonistic CLE signalling pathways that organizes tissue layer formation in the Arabidopsis root meristem.

分泌的 CLAVATA3/胚胎周围区域 （CLE） 肽配体通过冗余和交叉补偿 CLAVATA1 （CLV1） 型受体激酶进行信号传递，从而确定拟南芥芽分生组织的干细胞生态位。在根分生组织中，CLV1 同源物几乎没有任何分生组织 1 （BAM1） 和 BAM2 驱动 CLE13/16 介导的形成性分裂，从而产生地面组织层。在这里，我们报道了启动维管韧皮部谱系也需要 BAM1/2，并且在芽中观察到的 CLV1 型受体之间的交叉补偿在根中的作用不相似。相反，我们发现 BAM3 介导的 CLE45 信号拮抗韧皮部初始中的 BAM1/2 介导的 CLE11/12/13 信号，但在地面组织中不拮抗。我们进一步观察到韧皮部起始和分化的时空对比 CLE 信号要求，这些要求由 SHORT ROOT （SHR） 途径塑造。因此，我们的研究结果表明，在拟南芥根分生组织中组织层形成的不同和拮抗的 CLE 信号通路之间存在错综复杂的定量相互作用。