BES1 and BZR1 Redundantly Promote Phloem and Xylem Differentiation
BES1 and BZR1 Redundantly Promote Phloem and Xylem Differentiation
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DOI：
10.1093/pcp/pcy012
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发表时间：
2018-03
影响因子：
4.9
通讯作者：
M. Saito;Y. Kondo;H. Fukuda
中科院分区：
文献类型：
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作者：
M. Saito;Y. Kondo;H. Fukuda
血管发育是研究植物细胞分化的良好模型。木质部和韧皮部这两种传导组织源自称为前形成层/形成层细胞的常见干细胞。糖原合成酶激酶 3 蛋白 (GSK3) 通过抑制原形成层/形成层细胞分化为木质部或韧皮部细胞，在维持原形成层/形成层细胞方面发挥着至关重要的作用。我们之前设计了一种用于分析血管细胞分化的体外培养系统，名为 VISUAL（使用拟南芥叶的血管细胞诱导培养系统）。使用该系统，我们发现转录因子 BRI1-EMS-SUPPRESSOR 1 (BES1) 在木质部分化过程中充当 GSK3 的下游靶标。然而，BES1 在血管发育中的功能仍然很大程度上未知。在这里，我们发现，除了木质部分化之外，BES1 还积极调节 GSK3 下游的韧皮部分化。使用 VISUAL 进行的转录组分析证实，BES1 促进原形成层细胞双向分化为木质部和韧皮部细胞。使用 CRISPR/Cas9（成簇规则间隔短回文重复序列/CRISPR 相关蛋白 9）系统新生成的功能丧失突变体的遗传分析表明，BRASSINAZOLE RESISTANT 1 (BZR1) 是 BES1 最接近的同源物，在血管发育中与 BES1 一起发挥冗余功能。值得注意的是，BZR1 对血管细胞分化的影响比 BES1 弱，表明它们对该过程的贡献不同。总之，我们的研究结果表明，BES1 和 BZR1 是木质部和韧皮部细胞从血管干细胞分化的关键调节因子。
Vascular development is a good model for studying cell differentiation in plants. Two conductive tissues, the xylem and phloem, are derived from common stem cells known as procambial/cambial cells. Glycogen synthase kinase 3 proteins (GSK3s) play crucial roles in maintaining procambial/cambial cells by suppressing their differentiation into xylem or phloem cells. We previously designed an in vitro culture system for analyzing vascular cell differentiation named VISUAL (Vascular cell Induction culture System Using Arabidopsis Leaves). Using this system, we found that the transcription factor BRI1-EMS-SUPPRESSOR 1 (BES1) functions as a downstream target of GSK3s during xylem differentiation. However, the function of BES1 in vascular development remains largely unknown. Here, we found that, in addition to xylem differentiation, BES1 positively regulates phloem differentiation downstream of GSK3s. Transcriptome analysis using VISUAL confirmed that BES1 promotes bi-directional differentiation of procambial cells into xylem and phloem cells. Genetic analysis of loss-of-function mutants newly generated using the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9) system revealed that BRASSINAZOLE RESISTANT 1 (BZR1), the closest homolog of BES1, functions in vascular development redundantly with BES1. Notably, BZR1 has a weaker impact on vascular cell differentiation than BES1, suggesting that they contribute differentially to this process. In conclusion, our findings indicate that BES1 and BZR1 are key regulators of both xylem and phloem cell differentiation from vascular stem cells.