Roy Choudhury Swarup, Johns Sarah M, Pandey Sona
Donald Danforth Plant Science Center St. Louis Missouri.
Plant Direct. 2019 Apr 15;3(4):e00135. doi: 10.1002/pld3.135. eCollection 2019 Apr.
Legumes develop root nodules that harbor endosymbiotic bacteria, rhizobia. These rhizobia convert nitrogen to ammonia by biological nitrogen fixation. A thorough understanding of the biological nitrogen fixation in legumes and its regulation is key to develop sustainable agriculture. It is well known that plant hormones affect nodule formation; however, most studies are limited to model legumes due to their suitability for in vitro, plate-based assays. Specifically, it is almost impossible to measure the effects of exogenous hormones or other additives during nodule development in crop legumes such as soybean as they have huge root system in soil. To circumvent this issue, the present research develops suitable media and growth conditions for efficient nodule development under in vitro, soil-free conditions in an important legume crop, soybean. Moreover, we also evaluate the effects of all major phytohormones on soybean nodule development under identical growing conditions. Phytohormones such as abscisic acid (ABA) and jasmonic acid (JA) had an overall inhibitory effect and those such as gibberellic acid (GA) or brassinosteroids (BRs) had an overall positive effect on nodule formation. This versatile, inexpensive, scalable, and simple protocol provides several advantages over previously established methods. It is extremely time- and resource-efficient, does not require special training or equipment, and produces highly reproducible results. The approach is expandable to other large legumes as well as for other exogenous additives.
豆科植物会形成根瘤，其中含有共生细菌——根瘤菌。这些根瘤菌通过生物固氮作用将氮转化为氨。深入了解豆科植物中的生物固氮作用及其调控机制是发展可持续农业的关键。众所周知，植物激素会影响根瘤的形成；然而，由于其适用于体外平板试验，大多数研究仅限于模式豆科植物。具体而言，在大豆等豆科作物的根瘤发育过程中，几乎无法测量外源激素或其他添加剂的影响，因为它们在土壤中有庞大的根系。为了解决这个问题，本研究为重要豆科作物大豆在无土体外条件下高效形成根瘤开发了合适的培养基和生长条件。此外，我们还在相同的生长条件下评估了所有主要植物激素对大豆根瘤发育的影响。脱落酸（ABA）和茉莉酸（JA）等植物激素对根瘤形成总体上具有抑制作用，而赤霉素（GA）或油菜素内酯（BRs）等植物激素对根瘤形成总体上具有促进作用。这种通用、廉价、可扩展且简单的方案比以前建立的方法具有多个优势。它极其节省时间和资源，不需要特殊培训或设备，并且能产生高度可重复的结果。该方法可扩展到其他大型豆科植物以及其他外源添加剂。
