Wang Chenchen, Gao Yang, Gong Wen, Laux Thomas, Li Sha, Xiong Feng
State Key Laboratory of Wheat Improvement, College of Life Science, Shandong Agricultural University, Tai'an, 271018, China.
Faculty of Biology, Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Schänzlestrasse 1, Freiburg, 79104, Germany.
New Phytol. 2025 Mar;245(5):2038-2051. doi: 10.1111/nph.20371. Epub 2024 Dec 27.
Protoderm formation is a crucial step in early embryo patterning in plants, separating the precursors of the epidermis and the inner tissues. Although key regulators such as ARABIDOPSIS THALIANA MERISTEM LAYER1 (ATML1) and PROTODERMAL FACTOR2 (PDF2) have been identified in the model plant Arabidopsis thaliana, the genetic pathways controlling protoderm specification remain largely unexplored. Here, we combined genetic, cytological, and molecular approaches to investigate the regulatory mechanisms of protoderm specification in Arabidopsis thaliana. We report a novel role of the β-importin KETCH1 in protoderm specification. KETCH1 loss-of-function leads to aberrant protoderm cell morphology and absent ATML1 transcription in embryos. We further demonstrate that KETCH1 directly interacts with an RNA Polymerase II (Pol-II) cofactor JANUS, mediating its nuclear accumulation. Furthermore, JANUS directly interacts with the WUS HOMEOBOX2 (WOX2) protein, which is critical for WOX2-activated ATML1 expression. Consequently, JANUS, KETCH1, and WOX2 loss-of-function results in similar protoderm defects. Our results identify the tripartite KETCH1/JANUS/WOX2 transcriptional module as a novel regulatory axis in Arabidopsis protoderm specification.
原表皮形成是植物早期胚胎模式形成中的关键步骤，它将表皮前体和内部组织分隔开来。尽管在模式植物拟南芥中已鉴定出关键调节因子，如拟南芥分生组织层1（ATML1）和原表皮因子2（PDF2），但控制原表皮特化的遗传途径在很大程度上仍未得到探索。在此，我们结合遗传学、细胞学和分子学方法来研究拟南芥中原表皮特化的调控机制。我们报道了β-输入蛋白KETCH1在原表皮特化中的新作用。KETCH1功能丧失导致胚胎中原表皮细胞形态异常且ATML1转录缺失。我们进一步证明，KETCH1直接与RNA聚合酶II（Pol-II）辅因子JANUS相互作用，介导其核积累。此外，JANUS直接与WUS同源盒2（WOX2）蛋白相互作用，而WOX2蛋白对于WOX2激活的ATML1表达至关重要。因此，JANUS、KETCH1和WOX2功能丧失会导致类似的原表皮缺陷。我们的研究结果确定了三方KETCH1/JANUS/WOX2转录模块是拟南芥原表皮特化中的一个新的调控轴。
