多胺调控橡胶树死皮发生分子机制研究

Tapping panel dryness (TPD) is the primary limiting factor on the yielding increase of natural rubber, therefore solving TPD is a prerequisite for increasing natural rubber yields in rubber tree. It was reported that TPD was a programmed cell death (PCD) process and reactive oxygen species (ROS) metabolism, ubiquitin proteasome pathway, PCD and rubber biosynthesis were key pathways in TPD process. In this project, we firstly clone key genes involved in polyamine metabolism and investigate their expression profiles and bioinforatics analyses of their corresponding proteins. In order to reveal the relationships among polyamine, ROS, ethylene, PCD, and TPD in rubber tree, we will measure and compare the polyamine content, the activities of key enzymes involved in polyamine metabolism, ethylene and ROS contents, expression profiles of key genes involved in polyamine metabolism and the influence on PCD between the latex of healthy and TPD rubber trees under the control, polyamines and polyamine inhibitor treatments. In addition, we further study how polyamines regulate TPD in transgenic plants overexpressing key genes involved in polyamine metabolism by analyzing biological functions of key genes and the influences of their overexpression on ROS metablism, ethylene biosynthesis and PCD. The results will be helpful to not only further provide new insights into elucidating the molecular mechanisms involved in TPD, but also provide theoretical guidance for establishing effective and safe measures to prevent and treat TPD in rubber tree.

死皮是制约天然橡胶单产提高的主要限制因子，要提高橡胶树单产必须解决死皮问题。研究表明死皮是细胞程序化死亡(PCD)过程，活性氧(ROS)代谢、泛素蛋白酶体、PCD和橡胶生物合成为死皮发生关键调控途径。本项目拟从多胺调控死皮关键调控途径为切入点，采用生化和分子生物学方法，在克隆和分析多胺代谢途径关键基因表达及其编码蛋白生物信息学基础上，比较对照、外施多胺及多胺抑制剂条件下死皮和健康树胶乳多胺代谢途径关键酶活性、多胺、ROS和乙烯含量、多胺代谢途径关键基因表达模式及多胺和多胺抑制剂对PCD的影响，阐明多胺与橡胶树乙烯、ROS、PCD及死皮的关系；通过分析多胺代谢途径关键基因生物学功能及其过表达对ROS代谢、乙烯生物合成和PCD的影响，在生物体内解析多胺如何通过参与ROS代谢、乙烯生物合成及PCD调控橡胶树死皮。研究结果将为阐明橡胶树死皮发生机制提供新观点，也为制定有效死皮防控措施提供理论指导。

死皮是制约橡胶树单产提高的主要限制因子，要提高单产必须解决死皮问题。项目从多胺与死皮关键调控途径关系入手，解析多胺如何通过ROS代谢、乙烯合成及PCD调控橡胶树死皮。.研究发现多胺代谢途径基因与死皮相关，表达在不同组织、叶片发育时期存在变化，且受盐、低温、伤害等逆境调控。SAMDC基因5’UTR tiny和small uORF重叠且高度保守，small uORF对下游主基因起翻译抑制作用。外施多胺、多胺抑制剂可调控多胺代谢、乙烯、产排胶和PCD相关基因表达，推测多胺影响橡胶树乙烯合成、PCD和产排胶。外施多胺和多胺抑制剂后，健康树多胺分别升高和下降，ROS则分别下降和升高；除0和24 h Spm外，死皮树Put、Spd和Spm大于健康树，多胺代谢途径关键酶活性和乙烯含量变化不显著，说明外施多胺和多胺抑制剂可调控死皮和健康树多胺含量。.过表达HbSAMDC2烟草Put、Spd和Spm明显高于野生型，而过表达HbADC2烟草Put和Spm明显高于野生型，Spd无显著差异。对照与HbSAMDC2和HbADC2过表达烟草乙烯和ROS含量变化不大。在正常条件下，过表达HbSAMDC2和HbADC2表型无明显变化；盐胁迫下，过表达烟草和野生型生长均有延滞，在150 mM NaCl条件下HbSAMDC2能明显减弱盐胁迫对烟草的影响。NaCl为125和150 mM时，HbSAMDC2 转基因烟草苗鲜重显著大于野生型，说明SAMDC参与植物盐逆境反应。衣霉素处理后，过表达HbADC2烟草较野生型细胞死亡明显降低，说明HbADC2过表达可提高腐胺、精胺含量和抗氧化能力并降低细胞死亡，推测其可通过改变多胺含量和提高抗氧化能力调控细胞死亡参与死皮过程。.研究结果将为多胺调控橡胶树死皮提供新观点，有助于解析死皮机制，也为制定有效死皮防控措施提供理论指导。