Department of Plant Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
Department of Botany, Faculty of Science, Tanta University, Tanta, 31527, Egypt.
Planta. 2023 May 13;257(6):120. doi: 10.1007/s00425-023-04144-w.
Over-expression of Phytoglobin1 increases the viability of maize root stem cells to low oxygen stress through changes in auxin and jasmonic acid responses. Hypoxia inhibits maize (Zea mays L.) root growth by deteriorating the quiescent center (QC) stem cells of the root apical meristem. Over-expression of the Phytoglobin1 ZmPgb1.1 alleviates these effects through the retention of the auxin flow along the root profile required for the specification of the QC stem cells. To identify QC-specific hypoxia responses and determine whether ZmPgb1.1 exercises a direct role on QC stem cells, we performed a QC functionality test. This was done by estimating the ability of QCs to regenerate a root in vitro in a hypoxic environment. Hypoxia decreased the functionality of the QCs by depressing the expression of several genes participating in the synthesis and response of auxin. This was accompanied by a decrease in DR5 signal, a suppression of PLETHORA and WOX5, two markers of QC cell identity, and a reduction in expression of genes participating in JA synthesis and signaling. Over-expression of ZmPgb1.1 was sufficient to mitigate all these responses. Through pharmacological alterations of auxin and JA, it is demonstrated that both hormones are required for QC functionality under hypoxia, and that JA acts downstream of auxin during QC regeneration. A model is proposed whereby the ZmPgb1.1 maintenance of auxin synthesis in hypoxic QCs is determinant for the retention of their functionality, with JA supporting the regeneration of roots from the QCs.
过表达 Phytoglobin1 通过改变生长素和茉莉酸响应增加玉米根干细胞对低氧胁迫的活力。缺氧通过恶化根顶端分生组织静止中心 (QC) 干细胞来抑制玉米 (Zea mays L.) 根的生长。过表达 Phytoglobin1 ZmPgb1.1 通过保留根轮廓中生长素流来缓解这些影响，这是指定 QC 干细胞所必需的。为了鉴定 QC 特异性缺氧反应并确定 ZmPgb1.1 是否对 QC 干细胞发挥直接作用，我们进行了 QC 功能测试。这是通过估计 QC 在缺氧环境中体外再生根的能力来完成的。缺氧通过抑制参与生长素合成和响应的几个基因的表达来降低 QC 的功能。这伴随着 DR5 信号的减少，两个 QC 细胞身份标记物 PLETHORA 和 WOX5 的抑制，以及参与 JA 合成和信号转导的基因表达减少。过表达 ZmPgb1.1 足以缓解所有这些反应。通过生长素和 JA 的药理学改变，证明这两种激素在缺氧条件下都对 QC 功能是必需的，并且 JA 在 QC 再生过程中生长素的下游起作用。提出了一个模型，其中 ZmPgb1.1 在缺氧 QC 中维持生长素合成是维持其功能的决定因素，而 JA 则支持从 QC 再生根。
