Maize miRNA and target regulation in response to hormone depletion and light exposure during somatic embryogenesis

Abstract

Maize somatic embryogenesis (SE) is induced from the immature zygotic embryo in darkness and under the appropriate hormones' levels. Small RNA expression is reprogrammed and certain miRNAs become particularly enriched during induction while others, characteristic to the zygotic embryo, decrease. To explore the impact of different environmental cues on miRNA regulation in maize SE, we tested specific miRNA abundance and their target gene expression in response to photoperiod and hormone depletion for two different maize cultivars (VS-535 and H-565). The expression levels of miR156, miR159, miR164, miR168, miR397, miR398, miR408, miR528, and some predicted targets (SBP23, GA-MYB, CUC2, AGO1c, LAC2, SOD9, GR1, SOD1A, PLC) were examined upon staged hormone depletion in the presence of light photoperiod or darkness. Almost all examined miRNA, except miR159, increased upon hormone depletion, regardless photoperiod absence/presence. miR528, miR408, and miR398 changed the most. On the other hand, expression of miRNA target genes was strongly regulated by the photoperiod exposure. Stress-related miRNA targets showed greater differences between cultivars than development-related targets. miRNA/target inverse relationship was more frequently observed in darkness than light. Interestingly, miR528, but not miR159, miR168 or miR398, was located on polyribosome fractions suggesting a role for this miRNA at the level of translation. Overall our results demonstrate that hormone depletion exerts a great influence on specific miRNA expression during plant regeneration independently of light. However, their targets are additionally influenced by the presence of photoperiod. The reproducibility or differences observed for particular miRNA-target regulation between two different highly embryogenic genotypes provide clues for conserved miRNA roles within the SE process.

Epigenetic Regulation of Auxin-Induced Somatic Embryogenesis in Plants

“…Transcriptomic datasets on Zea mays embryogenic cultures have shown that the expression pattern of individual auxin-related miRNAs is dependent on the genotype and the age of a culture [66][67][68]78]. The diversity of the miRNA expression profiles in embryogenic cultures, for example, the up-vs. downregulation of the same miRNA, could reflect the complexity of the miRNA-mediated regulatory pathways that fine-tune the somatic cell transcriptome towards embryogenic development in response to specific endo-and exogenous culture factors.…”

Somatic Embryogenesis: Fundamental Aspects and Applications

“…Recently it was found that the induction process in maize is characterized by an enrichment of small RNA molecules that are involved with SE initiation (Chávez-Hernández et al 2015). Chávez-Hernández et al (2015) investigated the accumulation of certain miRNAs, and their predicted targets, during the SE of maize under different environmental conditions.…”

MicroRNAs Are Intensively Regulated during Induction of Somatic Embryogenesis in Arabidopsis

“…Similar to the widely documented involvement of miRNA molecules in plant development in vivo (Jin et al, 2013), the expression of miRNAs was reported during in vitro induced SE in several plant species including Citrus sinensis, Dimocarpus longan, Gossypium hirsutum, Larix kaempferi, Larix leptolepis, Liriodendron tulipifera × L. chinense, Manihot esculenta , and Zea mays (Zhang et al, 2012, 2014; Li et al, 2013; Lin and Lai, 2013; Yang et al, 2013; Chávez-Hernández et al, 2015; Wu et al, 2015; Lin et al, 2015a,b; Khatabi et al, 2016). Thus, the engagement of miRNAs in the embryogenic transition that is induced in vitro is assumed, although knowledge about the function of the specific miRNA in SE induction is very limited.…”