22‐Oxocholestanes SPGP4 and SPGP8: in Silico and in Vitro Study as Activators of Plant Growth Promotion

Abstract

The 22-oxocholestanes compounds have shown an outstanding plant growth promoting activity; they have similar bioactivity as brassinosteroids, so they are normally named as brassinosteroid analogs thinking that they also impact on the known receptor BRI1. However, in silico studies allow us to predict interactions with other receptors and thus it's possible to evaluate them, through receptors of gibberellins, auxins, jasmonates, strigolactones and the protein associated with the BRI1 gene. This article describes the bioactivity of structures SPGP4 and SPGP8 as plant growth-promoting compounds. Both structures present coupling energies and interactions at the same level as epibrassinolide in the protein associated with BRI1 gene. Additionally, interactions through the auxin pathway and to strigolactone receptor were found using selected tests. In the rice lamina tilt, a higher effect was obtained when SPGP4 and SPGP8 were compared to epibrassinolide, although in a lesser level vis à vis to homobrassinolide. In the same way, when SPGP4 and SPGP8 were tested in the Growth Root Model an activity as strigonolactones was observed, enhancing the relationship between the main and secondary roots. However, the growth of coleptiles, when applying auxins, compounds SPGP4 and SPGP8 did not reach the same level as controls. In the tests associated to gibberellins and jasmonic acid, an increased bioactivity was observed, although this behavior was not reflected from the in silico study, possibly due to secondary signaling cascades. This work demonstrates that the 22oxocolestane compounds SPGP4 and SPGP8 could be used as plant growth hormones, promoting several pathways.

Evaluation of the Plant Growth Regulator SPGP4 in Agricultural Crops: A Case Study in Oaxaca, México

“…The 22-Oxocholestane compounds, such as SPGP8 and SPGP4 (see Figure produced through a few reaction steps from natural spirostans. These compoun shown plant growth activity similar to that of the well-known brassinosteroids w plied at a greenhouse level [7,8]. Compound SPGP4 has recently been studied in tory assays and in controlled field experiments, detecting cell elongation, cell prol and cell differentiation.…”

“…The solution of SPGP4 was prepared according to the previously reported methodology [8] and validated by NMR spectroscopy (Figure S1). The SPGP4 stock solution (10 mg/mL) in acetone was prepared and maintained at 4 • C. From the stock solution, an aliquot was taken and diluted with water to prepare a 0.5 mg/L solution for seed immersion and foliar spraying.…”

“…So, synthesized 22-Oxocholestane compounds were evaluated at the greenhouse level to guarantee a positive effect in real culture conditions. Synthetic routes for brassinosteroids involve a high number of steps with low final yields of the order of 1.0% [7,8]. Through the structural modification of some steroids, Cuban researchers obtained the commercial Biobras-16 that tested positively in crops, finding excellent results that range from an increase of 31.7 to 61.3% in the seed mass of beans with one and two foliar sprays for the crop [9], and a 29.0% increase in the corn crop [10].…”

“…Compound SPGP4 has recently been studied in tory assays and in controlled field experiments, detecting cell elongation, cell prol and cell differentiation. From in silico studies, in addition to the activation of protein, an effect on auxins and strigolactone receptors was detected and eval vitro [8]. However, these studies need to be scaled up to an agricultural level to d their behavior in an uncontrolled, real environment and to determine the relation tween these pathways and their application to increase agricultural production The 22-Oxocholestane compounds, such as SPGP8 and SPGP4 (see Figure 1B), are produced through a few reaction steps from natural spirostans.…”

“…However, these studies need to be scaled up to an agricultural level to d their behavior in an uncontrolled, real environment and to determine the relation tween these pathways and their application to increase agricultural production The 22-Oxocholestane compounds, such as SPGP8 and SPGP4 (see Figure 1B), are produced through a few reaction steps from natural spirostans. These compounds have shown plant growth activity similar to that of the well-known brassinosteroids when applied at a greenhouse level [7,8]. Compound SPGP4 has recently been studied in laboratory assays and in controlled field experiments, detecting cell elongation, cell proliferation and cell differentiation.…”