The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries,but how it is initiated remains unclear.Here,we demonstrate with highthroughput infrared i...The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries,but how it is initiated remains unclear.Here,we demonstrate with highthroughput infrared imaging and 2-D clinostat treatment that,when gravity-induced root bending is absent,apical hook formation still takes place.In such scenarios,hook formation begins with a de novo growth asymmetry at the apical part of a straightly elongating hypocotyl.Remarkably,suchde novo asymmetric growth,but not the following hook enlargement,precedes the establishment of a detectable auxin response asymmetry,and is largely independent of auxin biosynthesis,transport and signaling.Moreover,we found that functional cortical microtubule array is essential for the following enlargement of hook curvature.When microtubule array was disrupted by oryzalin,the polar localization of PIN proteins and the formation of an auxin maximum became impaired at the to-be-hook region.Taken together,we propose a more comprehensive model for apical hook initiation,in which the microtubuledependent polar localization of PINs may mediate the instruction of growth asymmetry that is either stochastically taking place,induced by gravitropic response,or both,to generate a significant auxin gradient that drives the full development of the apical hook.展开更多
基金funded by the Southern University of Science and Technology for scientific research start-ups(Grant No.Y01226124 to H.G.)National Natural Science Foundation of China(Grant No.31700239 to Y.W.)+1 种基金Shenzhen Science and Technology Innovation Program(Grant No.JCYJ20170817105503416 to W.L.)Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes(SUSTech)(2019KSYS006 to H.G.)。
文摘The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries,but how it is initiated remains unclear.Here,we demonstrate with highthroughput infrared imaging and 2-D clinostat treatment that,when gravity-induced root bending is absent,apical hook formation still takes place.In such scenarios,hook formation begins with a de novo growth asymmetry at the apical part of a straightly elongating hypocotyl.Remarkably,suchde novo asymmetric growth,but not the following hook enlargement,precedes the establishment of a detectable auxin response asymmetry,and is largely independent of auxin biosynthesis,transport and signaling.Moreover,we found that functional cortical microtubule array is essential for the following enlargement of hook curvature.When microtubule array was disrupted by oryzalin,the polar localization of PIN proteins and the formation of an auxin maximum became impaired at the to-be-hook region.Taken together,we propose a more comprehensive model for apical hook initiation,in which the microtubuledependent polar localization of PINs may mediate the instruction of growth asymmetry that is either stochastically taking place,induced by gravitropic response,or both,to generate a significant auxin gradient that drives the full development of the apical hook.
