Format: ORAL

Qia Wang1, Steven M. Smith2,, Jinling Huang1,3,4,

1 Key Laboratory for Plant Diversity and Biogeography of East Asia, Yunnan Key Laboratory for Fungal Diversity and Green Development, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China 2 ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Natural Sciences, University of Tasmania, Hobart 7001, Australia 3 State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475004, China 4 Department of Biology, East Carolina University, Greenville, NC 27858, USA

Plants respond to environmental cues through physiological and developmental changes that are largely regulated by various signaling molecules. The phytohormones strigolactones (SLs) and exogenous compounds karrikins (KARs) are butenolides that influence multiple aspects of plant growth and development. D14 and KAI2 are members of the /-fold hydrolase superfamily and act as receptors of SLs and KARs, respectively. In this study, we found that the plant D14/KAI2 gene family was derived from bacterial gene RsbQ via horizontal gene transfer (HGT) during plant colonization of land. The D14/KAI2 and RsbQ proteins share conserved tertiary structures and functional features. We suggest that the acquisition of RsbQ by plant cells was fundamental to the formation of a butenolide sensing system, which provided a key innovation associated with the transition of green plants from aquatic to terrestrial environments. Recruitment of additional signal transduction components and gene duplication subsequently led to diverse SL and KAR signaling systems in land plants. This ?nding highlights the critical importance of HGT in plant evolution.