OsTIR1 and OsAFB2 Downregulation via OsmiR393 Overexpression Leads to More Tillers, Early Flowering and Less Tolerance to Salt and Drought in Rice

Abstract

The microRNA miR393 has been shown to play a role in plant development and in the stress response by targeting mRNAs that code for the auxin receptors in Arabidopsis. In this study, we verified that two rice auxin receptor gene homologs (OsTIR1 and OsAFB2) could be targeted by OsmiR393 (Os for Oryza sativa). Two new phenotypes (increased tillers and early flowering) and two previously observed phenotypes (reduced tolerance to salt and drought and hyposensitivity to auxin) were observed in the OsmiR393-overexpressing rice plants. The OsmiR393-overexpressing rice demonstrated hyposensitivity to synthetic auxin-analog treatments. These data indicated that the phenotypes of OsmiR393-overexpressing rice may be caused through hyposensitivity to the auxin signal by reduced expression of two auxin receptor genes (OsTIR1 and OsAFB2). The expression of an auxin transporter (OsAUX1) and a tillering inhibitor (OsTB1) were downregulated by overexpression of OsmiR393, which suggested that a gene chain from OsmiR393 to rice tillering may be from OsTIR1 and OsAFB2 to OsAUX1, which affected the transportation of auxin, then to OsTB1, which finally controlled tillering. The positive phenotypes (increased tillers and early flowering) and negative phenotypes (reduced tolerance to salt and hyposensitivity to auxin) of OsmiR393-overexpressing rice present a dilemma for molecular breeding.

The Accumulation of miRNAs Differentially Modulated by Drought Stress Is Affected by Grafting in Grapevine

“…Additional evidence supporting the stress-mediated regulation of miR393 is the presence of specific drought-induced ciselements in the promoter region of the related MIR gene (Devi et al, 2013). In Arabidopsis, miR393 is a key component of the auxin signaling cascade and tunes the expression of TIR1/AFB2 genes (Si-Ammour et al, 2011); this function also was confirmed in other plant species (Ferreira et al, 2012;Xia et al, 2012). In our study, however, the expression of the homologous grape target transcript, encoding the auxin-responsive factor TIR1-like, was inversely correlated to the abundance of miR393 only in leaves, implying that, in root, other stress-induced regulatory mechanisms could interfere with the miRNA inhibitory activity (Rogers and Chen, 2013).…”

A plant microRNA regulates the adaptation of roots to drought stress

“…This layer of regulation affects the auxin response in several developmental processes in plants when either the miRNA or its resistant targets are overexpressed [15,17]. Interestingly, the miR393 transcript level has been shown to be induced by ABA, cold, salt, or PEG treatment [11], implying a potential connection between stress and auxin signaling via this micro RNA.…”

The tae-miR408-Mediated Control of TaTOC1 Genes Transcription Is Required for the Regulation of Heading Time in Wheat

“…The miR156 and miR172 are two main factors that control the flowering time in the plant aging pathway (Huijser and Schmid, 2011;Yamaguchi and Abe, 2012;Wang, 2014). Other miRNA families including miR159, miR399, and OsmiR393 have also been shown to function in the control of flowering time (Achard et al, 2004;Kim et al, 2011;Xia et al, 2012). These miRNA-regulated pathways that control plant flowering time are themselves regulated by environmental factors, e.g.…”