Augustine Sruthy Maria, Cherian Anoop V, Syamaladevi Divya P, Subramonian N
Sugarcane Breeding Institute, ICAR, Coimbatore 641007, India
Present address: Max Planck Institute for Heart and Lungs Research, Bad Nauheim, Germany.
Plant Cell Physiol. 2015 Dec;56(12):2368-80. doi: 10.1093/pcp/pcv142. Epub 2015 Sep 30.
Plant growth during abiotic stress is a long sought-after trait especially in crop plants in the context of global warming and climate change. Previous studies on leaf epidermal cells have revealed that during normal growth and development, adjacent cells interdigitate anisotropically to form cell morphological patterns known as interlocking marginal lobes (IMLs), involving the cell wall-cell membrane-cortical actin continuum. IMLs are growth-associated cell morphological changes in which auxin-binding protein (ABP), Rho GTPases and actin are known to play important roles. In the present study, we investigated the formation of IMLs under drought stress and found that Erianthus arundinaceus, a drought-tolerant wild relative of sugarcane, develops such growth-related cell morphological patterns under drought stress. Using confocal microscopy, we showed an increasing trend in cortical F-actin intensity in drought-tolerant plants with increasing soil moisture stress. In order to check the role of drought tolerance-related genes in IML formation under soil moisture stress, we adopted a structural data mining strategy and identified indirect connections between the ABPs and heat shock proteins (HSPs). Initial experimental evidence for this connection comes from the high transcript levels of HSP70 observed in drought-stressed Erianthus, which developed anisotropic interdigitation, i.e. IMLs. Subsequently, by overexpressing the E. arundinaceus HSP70 gene (EaHSP70) in sugarcane (Saccharum spp. hybrid), we confirm the role of HSP70 in the formation of anisotropic interdigitation under drought stress. Taken together, our results suggest that EaHSP70 acts as a key regulator in the formation of anisotropic interdigitation in drought-tolerant plants (Erianthus and HSP70 transgenic sugarcane) under moisture stress in an actin-mediated pathway. The possible biological significance of the formation of drought-associated interlocking marginal lobes (DaIMLs) in sugarcane plants upon drought stress is discussed.
在非生物胁迫下的植物生长是一个长期以来备受关注的特性，尤其是在全球变暖和气候变化背景下的农作物中。先前对叶片表皮细胞的研究表明，在正常生长发育过程中，相邻细胞会各向异性地相互交错，形成称为互锁边缘叶（IMLs）的细胞形态模式，这涉及细胞壁-细胞膜-皮层肌动蛋白连续体。IMLs是与生长相关的细胞形态变化，已知生长素结合蛋白（ABP）、Rho GTP酶和肌动蛋白在其中发挥重要作用。在本研究中，我们调查了干旱胁迫下IMLs的形成，发现甘蔗的耐旱野生近缘种斑茅在干旱胁迫下会形成这种与生长相关的细胞形态模式。利用共聚焦显微镜，我们显示随着土壤水分胁迫的增加，耐旱植物中皮层F-肌动蛋白强度呈上升趋势。为了检验耐旱相关基因在土壤水分胁迫下IML形成中的作用，我们采用了结构数据挖掘策略，确定了ABP与热休克蛋白（HSPs）之间的间接联系。这种联系的初步实验证据来自于在遭受干旱胁迫且形成各向异性交错（即IMLs）的斑茅中观察到的HSP70高转录水平。随后，通过在甘蔗（甘蔗属杂交种）中过表达斑茅HSP70基因（EaHSP70），我们证实了HSP70在干旱胁迫下各向异性交错形成中的作用。综上所述，我们的结果表明，在水分胁迫下，EaHSP70在耐旱植物（斑茅和HSP70转基因甘蔗）中通过肌动蛋白介导的途径，作为各向异性交错形成的关键调节因子发挥作用。本文还讨论了甘蔗植株在干旱胁迫下形成干旱相关互锁边缘叶（DaIMLs）的可能生物学意义。
