背景回顾：Root angle in crops represents a key trait for efficient capture of soil resources. Root angle is determined by competing gravitropic versus antigravitropic offset (AGO) mechanisms. 

主要发现：Here we report a root angle regulatory gene termed ENHANCED GRAVITROPISM1 (EGT1) that encodes a putative AGO component, whose loss-of-function enhances root gravitropism. 

结果1-EGT1突变体表型：Mutations in barley and wheat EGT1 genes confer a striking root phenotype, where every root class adopts a steeper growth angle. 

结果2-EGT1编码蛋白及其自然变异：EGT1 encodes an F-box and Tubby domain-containing protein that is highly conserved across plant species. Haplotype analysis found that natural allelic variation at the barley EGT1 locus impacts root angle. 

结果3-EGT1作用机制：Gravitropic assays indicated that Hvegt1 roots bend more rapidly than wild-type. Transcript profiling revealed Hvegt1 roots deregulate reactive oxygen species (ROS) homeostasis and cell wall-loosening enzymes and cofactors. ROS imaging shows that Hvegt1 root basal meristem and elongation zone tissues have reduced levels. Atomic force microscopy measurements detected elongating Hvegt1 root cortical cell walls are significantly less stiff than wild-type. 

结果4-EGT1表达模式：In situ analysis identified HvEGT1 is expressed in elongating cortical and stele tissues, which are distinct from known root gravitropic perception and response tissues in the columella and epidermis, respectively.  

结论：We propose that EGT1 controls root angle by regulating cell wall stiffness in elongating root cortical tissue, counteracting the gravitropic machinery’s known ability to bend the root via its outermost tissues. We conclude that root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism. 

在作物中，根的角度是一个作用于高效获取土壤中营养物质的关键性状。根的角度受到重力和反重力抵消（AGO）机制之间的竞争性作用。本文中，作者报道了一个根角度调控基因EGT1，该基因编码一个假定的AGO组分，其功能缺失突变能够增强根的向重力性。在大麦和小麦中突变EGT1基因能够引起显著的根表型改变，具体表现在几乎每个根都具有更陡的生长角度。EGT1基因编码一个含有F-box和Tubby结构域的蛋白，在不同植物物种间高度保守。单倍型分析显示，大麦EGT1位点上的自然等位变异影响了根的角度。重力实验显示Hvegt1突变体的根要比野生型弯曲得更快。转录图谱显示，Hvegt1突变体的根解除了对ROS内稳态、细胞壁松弛酶及辅因子的调控。ROS呈像显示，Hvegt1突变体根基部分生组织和伸长区组织的ROS积累水平降低。原子力显微镜测量显示，Hvegt1突变体中正在伸长的根皮层细胞明显比野生型更加坚硬，不容易弯曲。原位分析显示，HvEGT1在根中正在伸长的皮层细胞和中柱组织中表达，但是目前已知的根重力感知和响应因子分别在小柱和表皮组织中。作者提出，EGT1通过调控根中正在伸长的皮层细胞的细胞壁坚硬程度，抵消了目前已知的根向重力性机制通过根最外层组织来弯曲根的能力，从而控制根的生长角度。作者总结道，在谷类作物中EGT1基因通过一个反重力性机制，控制了根的角度。

 Malcolm Bennett