A KARRIKIN INSENSITIVE2 paralog in lettuce mediates highly sensitive germination responses to karrikinolide
A KARRIKIN INSENSITIVE2 paralog in lettuce mediates highly sensitive germination responses to karrikinolide
复制标题
DOI：
10.1101/2021.10.13.464162
复制
发表时间：
2021-10
期刊：
影响因子：
--
通讯作者：
Stephanie E. Martinez;Caitlin E. Conn;Angelica M. Guercio;C. Sepulveda;Christopher J. Fiscus;Daniel Koenig;N. Shabek;David C. Nelson
中科院分区：
文献类型：
--
作者：
Stephanie E. Martinez;Caitlin E. Conn;Angelica M. Guercio;C. Sepulveda;Christopher J. Fiscus;Daniel Koenig;N. Shabek;David C. Nelson
Karrikins（KARs）是烟雾中的化学物质，可以促进许多植物的发芽。莴苣大急流城（莴苣），在纳摩尔karrikinase（KAR 1）的存在下发芽。我们发现莴苣对KAR 2或合成独脚金内酯类似物rac-GR 24的混合物的反应要小得多。我们研究了生菜中选择性和敏感性KAR 1感知的分子基础。莴苣基因组含有两个KARRIKIN INSENSITIVE 2（KAI 2）拷贝，KAI 2是拟南芥中KAR反应所需的受体。LsKAI 2b比LsKAI 2a在干燥的瘦果中和在种子吸胀的早期阶段更高地表达。通过拟南芥中的跨物种互补测定，我们发现LsKAI 2b赋予对KAR 1的稳健响应，但LsKAI 2a不。因此，LsKAI 2b可能介导莴苣中的KAR 1应答。我们比较了同源模型的配体结合口袋的KAI 2蛋白从生菜和火的追随者，Emmenanthe penduliflora。这将口袋残基96、124、139和161鉴定为影响KAI 2的配体特异性的候选物。进一步支持这些残基的重要性，发现通过更广泛的比较口袋残基的保守性之间的324个pseudodKAI 2蛋白。我们测试了在拟南芥KAI 2中这四个位置的取代的效果，发现可以实现对KAR 1，KAR 2和rac-GR 24的广泛响应。
Karrikins (KARs) are chemicals in smoke that can enhance germination of many plants. Lactuca sativa cv. Grand Rapids (lettuce), germinates in the presence of nanomolar karrikinolide (KAR1). We found that lettuce is much less responsive to KAR2 or a mixture of synthetic strigolactone analogs, rac-GR24. We investigated the molecular basis of selective and sensitive KAR1 perception in lettuce. The lettuce genome contains two copies of KARRIKIN INSENSITIVE2 (KAI2), a receptor that is required for KAR responses in Arabidopsis thaliana. LsKAI2b is more highly expressed than LsKAI2a in dry achenes and during early stages of seed imbibition. Through cross-species complementation assays in Arabidopsis we found that LsKAI2b confers robust responses to KAR1, but LsKAI2a does not. Therefore, LsKAI2b likely mediates KAR1 responses in lettuce. We compared homology models of the ligand-binding pockets of KAI2 proteins from lettuce and a fire follower, Emmenanthe penduliflora. This identified pocket residues 96, 124, 139, and 161 as candidates that influence the ligand-specificity of KAI2. Further support for the significance of these residues was found through a broader comparison of pocket residue conservation among 324 asterid KAI2 proteins. We tested the effects of substitutions at these four positions in Arabidopsis thaliana KAI2 and found that a broad array of responses to KAR1, KAR2, and rac-GR24 could be achieved.