Abstract
Rice allelopathy is a natural method of weed control that is regarded as an eco-friendly practice in agroecology. The allelopathic potential of rice is regulated by various genes, including those that encode transcription factors. Our study characterized a MYB transcription factor, OsMYB57, to explore its role in the regulation of rice allelopathy. Increasing the expression of OsMYB57 in rice using the transcription activator VP64 resulted in increased inhibitory ratios against barnyardgrass. The gene expression levels of OsPAL, OsC4H, OsOMT, and OsCAD from the phenylpropanoid pathway were also up-regulated, and the content of l-phenylalanine increased. Chromatin immunoprecipitation incorporated with HiSeq demonstrated that OsMYB57 transcriptionally regulated a mitogen-activated protein kinase (OsMAPK11); in addition, OsMAPK11 interacted with OsPAL2;3. The expression of OsPAL2;3was higher in the allelopathic rice PI312777 than in the non-allelopathic rice Lemont, and OsPAL2;3 was negatively regulated by Whirly transcription factors. Moreover, microbes with weed-suppression potential, including Penicillium spp. and Bacillus spp., were assembled in the rhizosphere of the rice accession Kitaake with increased expression of OsMYB57, and were responsible for phenolic acid induction. Our findings suggest that OsMYB57 positively regulates rice allelopathy, providing an option for the improvement of rice allelopathic traits through genetic modification.
Highlights
Allelopathy is a biological phenomenon, typical of certain plants, algae, and microorganisms (Reigosa et al, 2006), that involves inhibitory or stimulatory effects of one organism on another.This phenomenon can influence organism growth, survival, and reproduction through the secretion of allelochemicals or their release into the environment (Rice, 1984)
The capacity for suppression on the root length of barnyardgrass was enhanced at a ratio of approximately 20–39% for rice with increased OsMYB57 expression levels compared with a ratio of –0.4–2.3% for wild type (WT) Kitaake in agar culture medium (Fig. 1B)
The expression of the genes encoding momilactone-A synthase (OsMAS) and syn-pimara-7, 15-diene synthase (OsKSL4) from the momilactone pathway were down-regulated by a factor of 0.67 and 0.42, respectively, in OsMYB57VP64 compared with Kitaake
Summary
Allelopathy is a biological phenomenon, typical of certain plants, algae, and microorganisms (Reigosa et al, 2006), that involves inhibitory or stimulatory effects of one organism on another.This phenomenon can influence organism growth, survival, and reproduction through the secretion of allelochemicals or their release into the environment (Rice, 1984). Allelochemicals belong to the secondary plant metabolites, and the role of several groups of secondary metabolites, such as phenolic acids and terpenoids, in allelopathy has been documented (Maqbool et al, 2013; Soltys et al, 2013; Einhellig, 2018) They are predominantly derived from the phenylpropanoid metabolic and isoprenoid biosynthetic pathways and their associated branch paths (Verpoorte, 2000). Phenolic acids secreted from the root tissue were found to interact with specific microorganisms in the rice rhizosphere (e.g. Myxococcus xanthus) to increase the inhibition of weeds This inhibition indicates the vital role of the interaction of M. xanthus and phenolic acids in rice allelopathy in the field (Fang et al, 2015).These compounds are known to be derived from the phenylpropanoid metabolic pathway
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