School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA, 24061, USA.
Department of Plant Sciences, University of Tennessee, Knoxville, TN, 37996, USA.
Plant Mol Biol. 2019 Jun;100(3):303-317. doi: 10.1007/s11103-019-00861-7. Epub 2019 Apr 3.
Overexpression of the poplar PP2C protein phosphatase gene PtrHAB2 resulted in increased tree height and altered leaf morphology and phyllotaxy, implicating PP2C phosphatases as growth regulators functioning under favorable conditions. We identified and studied Populus trichocarpa genes, PtrHAB1 through PtrHAB15, belonging to the clade A PP2C family of protein phosphatases known to regulate abscisic acid (ABA) signaling. PtrHAB1 through PtrHAB3 and PtrHAB12 through PtrHAB15 were the most highly expressed genes under non-stress conditions. The poplar PP2C genes were differentially regulated by drought treatments. Expression of PtrHAB1 through PtrHAB3 was unchanged or downregulated in response to drought, while all other PtrHAB genes were weakly to strongly upregulated in response to drought stress treatments. Yeast two-hybrid assays involving seven ABA receptor proteins (PtrRCAR) against 12 PtrHAB proteins detected 51 interactions involving eight PP2Cs and all PtrRCAR proteins with 22 interactions requiring the addition of ABA. PtrHAB2, PtrHAB12, PtrHAB13 and PtrHAB14 also interacted with the sucrose non-fermenting related kinase 2 proteins PtrSnRK2.10 and PtrSnRK2.11, supporting conservation of a SnRK2 signaling cascade regulated by PP2C in poplar. Additionally, PtrHAB2, PtrHAB12, PtrHAB13 and PtrHAB14 interacted with the mitogen-activated protein kinase protein PtrMPK7. Due to its interactions with PtrSnRK2 and PtrMPK7 proteins, and its reduced expression during drought stress, PtrHAB2 was overexpressed in poplar to test its potential as a growth regulator under non-stress conditions. 35S::PtrHAB2 transgenics exhibited increased growth rate for a majority of transgenic events and alterations in leaf phyllotaxy and morphology. These results indicate that PP2Cs have additional roles which extend beyond canonical ABA signaling, possibly coordinating plant growth and development in response to environmental conditions.
杨树 PP2C 蛋白磷酸酶基因 PtrHAB2 的过表达导致树高增加，叶片形态和叶序改变，暗示 PP2C 磷酸酶作为在有利条件下发挥作用的生长调节剂。我们鉴定并研究了毛果杨基因 PtrHAB1 到 PtrHAB15，它们属于 A 族 PP2C 家族的蛋白磷酸酶，已知其调节脱落酸 (ABA) 信号。在非胁迫条件下，PtrHAB1 到 PtrHAB3 和 PtrHAB12 到 PtrHAB15 是表达量最高的基因。干旱处理对杨树 PP2C 基因有不同的调控作用。干旱胁迫下，PtrHAB1 到 PtrHAB3 的表达不变或下调，而所有其他 PtrHAB 基因则被弱至强地上调。涉及 7 个 ABA 受体蛋白 (PtrRCAR) 的酵母双杂交实验针对 12 个 PtrHAB 蛋白，检测到涉及 8 个 PP2C 和所有 PtrRCAR 蛋白的 51 个相互作用，其中 22 个相互作用需要添加 ABA。PtrHAB2、PtrHAB12、PtrHAB13 和 PtrHAB14 还与蔗糖非发酵相关激酶 2 蛋白 PtrSnRK2.10 和 PtrSnRK2.11 相互作用，支持 ABA 调控的 SnRK2 信号级联在杨树中的保守性。此外，PtrHAB2、PtrHAB12、PtrHAB13 和 PtrHAB14 与丝裂原活化蛋白激酶蛋白 PtrMPK7 相互作用。由于其与 PtrSnRK2 和 PtrMPK7 蛋白的相互作用，以及在干旱胁迫下的表达减少，PtrHAB2 在杨树中过表达，以测试其在非胁迫条件下作为生长调节剂的潜力。35S::PtrHAB2 转基因表现出大多数转基因事件的生长速率增加，以及叶片叶序和形态的改变。这些结果表明，PP2C 具有超出经典 ABA 信号的额外作用，可能协调植物生长和发育以响应环境条件。
