Hormonal response of Acutodesmus obliquus exposed to combined treatment with 24-epibrassinolide and lead

Abstract

Phytohormones play key roles in many aspects of plant growth and development, as well as in resistance to abiotic stresses. The presence of heavy metal limits phytohormone endogenous level; however, the application of brassinosteroids (BRs) restores phytohormone homeostasis and reduces unfavorable consequences of heavy metal on plant growth. Therefore, the aim of this study was to (1) broaden previously published analyses/findings to study the effect of 24-epibrassinolide (EBL) and/or lead (Pb) on Acutodesmus obliquus phytohormone level after 5 days of cultivation using LC-QToF-MS quantification technique and (2) extend the total amount of quantified phytohormones in A. obliquus. The study confirmed that exogenous EBL increased the contents of gibberellin A3 (GA3), auxins (AXs) (indole-3-acetic acid, phenylacetic acid), BRs brassinolide, 24-epibrassinolide (EBL), 28-homobrassinolide, castasterone, 24-epicastasterone, typhasterol, cathasterone, 6-deoxotyphasterol, as well as different types of cytokinins (CKs): free bases, ribosides, and conjugates (N- and O-glucosides). On the other hand, treatment with Pb had an opposite effect on BRs, GA3, AXs, and free bases, as well as ribosides of CKs. The abscisic acid (ABA) level decreased under EBL treatment but increased in response to Pb stress. The level of N-glucosides, as well as O-glucosides of CKs, also significantly increased in response to Pb alone. Interestingly, the co-application of EBL and Pb led to an increase in BRs, GA3, AXs, and CKs content in the algae. Principal component analysis revealed that based on treatments, increase of GA3, BRs, and AXs was found to be in the following order: 1 μM EBL > 0.01 μM Pb + 1 μM EBL > 500 μM Pb + 1 μM EBL > control > 0.01 μM Pb > 500 μM Pb. Moreover, very strong significant linear relations between almost all studied AXs and BRs were noted. Summarizing, this research did not only allow to detect the occurrence of ABA, GA3, AXs, BRs, and CKs in A. obliquus for the first time but also to study the combined action of EBL and Pb, as well as compare it with treatment alone.

Brassinolide Enhances the Level of Brassinosteroids, Protein, Pigments, and Monosaccharides in Wolffia arrhiza Treated with Brassinazole

“…In other reports, the levels and the profiles of BRs varied in dependence on family, species, or environment. Among freshwater plants, eight various BRs were detected in A. obliquus [ 45 ], while the presence of the most active BL and CS was confirmed in many algal strains [ 46 , 47 ]. Whereas, among freshwater angiosperms, the level of BRs was not studied.…”

Phytohormones enhance heavy metal responses inEuglena gracilis: evidence from uptake of Ni, Pb and Cd and linkages to hormonomic and metabolomic dynamics

“…To this end, they may sequester metals using thiol-compounds (Cys, gammaglutamyl cysteine (γEC), GSH and Poly-GSH) and mitigate damage through activation of antioxidants (superoxide dismutase-SOD, catalase-CAT, peroxidase-POD), or produce global stress response/defense compounds (i.e., transcriptional factors, cellular metal transporters, mitogen-activated protein kinases-MAPKs, chaperones) ( Khatiwada et al, 2020; Hernández-Garnica et al, 2021) . These strategies can be regulated by phytohormones such as cytokinins (CKs) and abscisic acid (ABA) (Piotrowska-Niczyporuk et al, 2020; Talarek-Karwel et al, 2020) . Recent studies have started to suggest that CKs and ABA can regulate cellular redox balance, nutrients and other phytohormones in HM stress responses (Piotrowska-Niczyporuk et al, 2012, 2018, 2020; Talarek-Karwel et al, 2020 ).…”

“…These strategies can be regulated by phytohormones such as cytokinins (CKs) and abscisic acid (ABA) (Piotrowska-Niczyporuk et al, 2020; Talarek-Karwel et al, 2020) . Recent studies have started to suggest that CKs and ABA can regulate cellular redox balance, nutrients and other phytohormones in HM stress responses (Piotrowska-Niczyporuk et al, 2012, 2018, 2020; Talarek-Karwel et al, 2020 ). Given this scenario, our study has detailed an effect of CK- and ABA-induced enhancements of metal uptake, and underlying mechanisms of hormone cross-talk and metal acclimation pathways.…”

“…Discovering additional crosstalk mechanisms among various hormones (ABA, CK, gibberellins (GAs), auxins, salicylic acid (SA), jasmonic acid (JA)) in coordinating growth under metal stress is an important theme in the field of algal bioremediation ( Nguyen et al, 2020 ). Hormonal crosstalk is thought to play major roles in HM tolerance via activation of phytochelatin biosynthesis, stimulation of antioxidant apparatus (i.e., carotenoids, ascorbate peroxidase, catalase, superoxide dismutase), or stimulation of protective compounds (e.g., proline, astaxanthin, pigments) ( Piotrowska-Niczyporuk et al, 2020; Talarek-Karwel et al, 2020 ).…”

Is Genetic Engineering a Route to Enhance Microalgae-Mediated Bioremediation of Heavy Metal-Containing Effluents?

“…Stimulating microalgae with exogenous GA and auxin was shown to mitigate HM stress by regulating photosynthesis, besides fatty acid and antioxidant metabolism [ 56 , 237 , 239 ]. Similarly, ABA and Br alleviated Pb, Cd, and Cu stress in A. obliquus and C. vulgaris cells, via induction of PC biosynthesis [ 238 , 240 , 241 ]. Furthermore, ET and SA effectively scavenged and detoxified ROS in C. vulgaris and Haematococcus pluvialis under HM stress, by inducing Pro/astaxanthin and SOD/CAT encoding genes [ 242 , 243 , 244 ].…”