Temporal Control of Trichome Distribution by MicroRNA156-TargetedSPLGenes inArabidopsis thaliana   

Abstract

The production and distribution of plant trichomes is temporally and spatially regulated. After entering into the flowering stage, Arabidopsis thaliana plants have progressively reduced numbers of trichomes on the inflorescence stem, and the floral organs are nearly glabrous. We show here that SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes, which define an endogenous flowering pathway and are targeted by microRNA 156 (miR156), temporally control the trichome distribution during flowering. Plants overexpressing miR156 developed ectopic trichomes on the stem and floral organs. By contrast, plants with elevated levels of SPLs produced fewer trichomes. During plant development, the increase in SPL transcript levels is coordinated with the gradual loss of trichome cells on the stem. The MYB transcription factor genes TRICHOMELESS1 (TCL1) and TRIPTYCHON (TRY) are negative regulators of trichome development. We show that SPL9 directly activates TCL1 and TRY expression through binding to their promoters and that this activation is independent of GLABROUS1 (GL1). The phytohormones cytokinin and gibberellin were reported to induce trichome formation on the stem and inflorescence via the C2H2 transcription factors GIS, GIS2, and ZFP8, which promote GL1 expression. We show that the GIS-dependent pathway does not affect the regulation of TCL1 and TRY by miR156-targeted SPLs, represented by SPL9. These results demonstrate that the miR156-regulated SPLs establish a direct link between developmental programming and trichome distribution.

Seasonal Regulation of Petal Number

“…7A), which represent three subgroups of miRNA-regulated SPL genes (Guo et al, 2008). These genes were also chosen because they contribute to the regulation of sepal trichome number in Arabidopsis (Shikata et al, 2009;Yu et al, 2010;Wei et al, 2012). We found that ChSPL3 expression increased stepwise from vegetative to early inflorescence to anthesis stages of development, while ChSPL9 expression increased from early inflorescence to anthesis stages (Fig.…”

“…This variation is strongly influenced by plant ageing, such that petal number per flower declines as a plant ages. Another phenotype that shows this temporal trend is the declining number of trichomes on the abaxial side of sepals as a plant ages (Shikata et al, 2009;Yu et al, 2010), and both of these age-dependent traits share a common genetic basis in C. hirsuta . Therefore, common QTL affect both petal number and sepal trichome number and act in an age-dependent manner.…”

Transcriptional control of flavonoid biosynthesis

“…20,21 These plantspecific SPB-box proteins are known to influence a large array of developmental processes in Arabidopsis, such as promoting the juvenile-to-adult phase transition by activating miR172, inducing flowering via activating LEAFY and the MADS box genes, inhibiting trichome initiation on floral organs through activating TCL1, as well as concertedly controlling male fertility. [21][22][23][24] Recently, the miR156/157-targeted SPLs have been shown to affect metabolic fluxes through the branched flavonoid biosynthetic pathway. 4 Dihydroflavonols serve as common precursors of flavonols and anthocyanins and can be oxidized either by FLS to form flavonols or reduced by DFR to produce leucoanthocyanidins in the first dedicated step for anthocyanin biosynthesis (Fig.…”

High-throughput sequencing-based genome-wide identification of microRNAs expressed in developing cotton seeds

“…Consistent with our previous research [4], the mRNAs of SPL9 were cleaved within the complementary region of GhmiR156. The target of miR156, SPL9, has been reported to play critical roles in the temporal control of trichome distribution in Arabidopsis thaliana [25].…”