一种基于亚磷酸盐及其脱氢酶的植物磷利用和杂草控制系统的建立

Establishment of a plant phosphorus utilization and weed control system based on phosphite and its dehydrogenase

摘要:

磷是植物生长发育所必需的大量营养元素之一。土壤中存在大量的正磷酸盐 (Pi)，但由于土壤化学和微生物转化使得土壤可利用磷的浓度并不高。土壤缺磷以及杂草的抗除草剂能力已成为当前农业可持续发展的重要限制因素，所以提高植物对土壤磷的吸收利用能力或寻求可替代正磷酸盐的磷肥以及开发新型杂草控制系统已成为亟待解决的问题。自然界中亚磷酸盐 (Phi) 是含量仅次于正磷酸盐的磷源，但仅在某些细菌中能被专一性的亚磷酸盐脱氢酶 (PTDH) 氧化利用，对植物的生长发育则具有抑制作用。利用这一特性，将从土壤宏基因组中直接扩增到的假单胞菌PTDH基因PsPtx通过农杆菌侵染法转入烟草中，并通过RT-PCR、垂直板幼苗生长、显性标记和生长竞争实验分析PsPtx转基因烟草的基因表达以及在Phi胁迫条件下的特性。结果显示，PsPtx在其转基因植株的根茎叶组织中都有几乎相同水平的表达；PsPtx转基因烟草不但能解除Phi对植物的毒害作用，并将它氧化成可用的Pi作为生长发育所需的磷源，而且在Phi胁迫条件下较野生型烟草有相当明显的生长竞争优势；另外PsPtx还具备成为植物遗传转化显性选择标记的优良特质。因此，PsPtx基因编码的亚磷酸盐脱氢酶可用于开发一种基于亚磷酸盐为磷肥和除草剂的植物磷利用和杂草控制系统，为当前农作物转基因研究存在的一些重大问题提供一个有效解决方案。

Abstract:

Nowadays, available phosphorus (P) deficiency in soil and weed resistance to herbicides have emerged as two severe limiting factors for sustainable agriculture. Therefore, it is of urgent needs to improve plant absorption/utilization ability of the soil P, seek phosphate (Pi)-alternative P fertilizers, and develop new forms of weed control systems. Phosphite (Phi), as a P resource of relatively high amount only less than Pi in Earth, can be converted to utilizable Pi uniquely in some bacterial species by oxidization via its specific dehydrogenase (PTDH), but inhibits plant growth and development. This implies that Phi might rather become a suitable P fertilizer for plants if introducing a PTDH detoxifier from bacteria. Herein, we created the transgenic tobaccos harboring a Pseudomonas PTDH gene (PsPtx) amplified from the soil metagenome previously. RT-PCR showed that the exotic PsPtx gene could express similarly in root, stem and leaf tissues of all transgenic lines. PsPtx transgenic tobaccos could utilize Phi by oxidization as the sole Pi supply, and also outperformed wild-type tobacco with a remarkably dominant growth under Phi stress conditions. Moreover, the PsPtx gene was preliminarily evaluated with a notable quality as a potential candidate of the selection marker in plant genetic transformation. Conclusively, PsPtx and its encoded phosphite dehydrogenase might be applicable for developing a dual system of plant phosphorus utilization and weed control using Phi as P fertilizer and herbicide, and provide an effectual solution to some obstacles in the current crop transgenic studies.