Root system architecture is influenced by gravity.How the root senses gravity and directs its orientation,so-called gravitropism,is not only a fundamental question in plant biology but also theoretically impor-tant for genetic improvement of crop root architecture.However,the mechanism has not been elucidated in most crops.We characterized a rice agravitropism allele,wavy root 1(war1),a loss-of-function allele in OsPIN2,which encodes an auxin efflux transporter.With loss of OsPIN2 function,war1 leads to altered root system architecture including wavy root,larger root distribution angle,and shallower root system due to the loss of gravitropic perception in root tips.In the war1 mutant,polar auxin transport was dis-rupted in the root tip,leading to abnormal auxin levels and disturbed auxin transport and distribution in columella cells.Amyloplast sedimentation,an important process in gravitropic sensing,was also decreased in root tip columella cells.The results indicated that OsPIN2 controls gravitropism by finely regulating auxin transport,distribution and levels,and amyloplast sedimentation in root tips.We iden-tified a novel role of OsPIN2 in regulating ABA biosynthesis and response pathways.Loss of OsPIN2 func-tion in the war1 resulted in increased sensitivity to ABA in seed germination,increased ABA level,changes in ABA-associated genes in roots,and decreased drought tolerance in the seedlings.These results suggest that the auxin transporter OsPIN2 not only modulates auxin transport to control root gravitropism,but also functions in ABA signaling to affect seed germination and root development,probably by mediating crosstalk between auxin and ABA pathways.

Wenqiang Li;Minjuan Zhang;Lei Qiao;Yunbo Chen;Dapeng Zhang;Xiuqing Jing;Pengfei Gan;Yangbin Huang;Junru Gao;Wenting Liu;Chunhai Shi;Hongchang Cui;Haifeng Li;Kunming Chen

State Key Laboratory of Crop Stress Biology in Arid Areas,College of Life Sciences,Northwest A&F University,Yangling 712100,Shaanxi,China;The Sericultural and Silk Research Institute,College of Animal Science and Technology,Northwest A&F University,Yangling 712100,Shaanxi,China;College of Agronomy,Northwest A&F University,Yangling 712100,Shaanxi,China;Department of Agronomy,College of Agriculture and Biotechnology,Zhejiang University,Hangzhou 310058,Zhejiang,China;Department of Biological Science,Florida State University,Tallahassee,FL 32306,USA

作物学报（英文版）

[1]Wenqiang Li;Minjuan Zhang;Lei Qiao;Yunbo Chen;Dapeng Zhang;Xiuqing Jing;Pengfei Gan;Yangbin Huang;Junru Gao;Wenting Liu;Chunhai Shi;Hongchang Cui;Haifeng Li;Kunming Chen-.Characterization of wavy root 1,an agravitropism allele,reveals the functions of OsPIN2 in fine regulation of auxin transport and distribution and in ABA biosynthesis and response in rice(Oryza sativa L.))[J].作物学报（英文版）,2022(04):980-992

agravitropism,OsPIN2,gravitropism,war1,gravitropic,rupted,columella,Amyloplast,amyloplast

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