Modulation of miR156 to identify traits associated with vegetative phase change in tobacco (Nicotiana tabacum)

Abstract

After germination, plants progress through juvenile and adult phases of vegetative development before entering the reproductive phase. The character and timing of these phases vary significantly between different plant species, which makes it difficult to know whether temporal variations in various vegetative traits represent the same, or different, developmental processes. miR156 has been shown to be the master regulator of vegetative development in plants. Overexpression of miR156 prolongs the juvenile phase of development, whereas knocking-down the level of miR156 promotes the adult phase of development. Therefore, artificial modulation of miR156 expression is expected to cause corresponding changes in vegetative-specific traits in different plant species, particularly in those showing no substantial difference in morphology during vegetative development. To identify specific traits associated with the juvenile-to-adult transition in tobacco, we examined the phenotype of transgenic tobacco plants with elevated or reduced levels of miR156. We found that leaf shape, the density of abaxial trichomes, the number of leaf veins, the number of stomata, the size and density of epidermal cells, patterns of epidermal cell staining, the content of chlorophyll and the rate of photosynthesis, are all affected by miR156. These newly identified miR156-regulated traits therefore can be used to distinguish between juvenile and adult phases of development in tobacco, and provide a starting point for future studies of vegetative phase change in the family Solanaceae.

High miR156 Expression Is Required for Auxin-Induced Adventitious Root Formation via MxSPL26 Independent of PINs and ARFs in Malus xiaojinensis

“…The expression level of miR156 was decreased during juvenile to adult phase change (Du et al, 2015; Ji et al, 2016). However, the effect of miR156 on adventitious root formation barely rated a mention in previous reports (Zhang et al, 2011; Feng et al, 2016; Massoumi et al, 2017). Although, miR156-targeted SPLs are known to control varied physiological and developmental processes (Wang et al, 2008; Shikata et al, 2009; Yu et al, 2010, 2015; Gou et al, 2011), with which the miR156-targeted SPL gene member is associated with adventitious rooting and how miR156 interacts with other rooting regulatory factors such as IAA are so far not fully understood to date.…”

“…When miR156 level was manipulated via transformation with a 35S:MIR156 construct in tomato, tobacco, or Arabidopsis , the adventitious rooting increased (Zhang et al, 2011; Feng et al, 2016; Massoumi et al, 2017). In the present study, the miR156 expression level was manipulated in transgenic tobacco to analyze how miR156/SPL modules are involved in adventitious rooting.…”

“…Auxin and miR156 are both involved in adventitious root development (Zhang et al, 2011; Feng et al, 2016; Steffens and Rasmussen, 2016; Massoumi et al, 2017). However, the interaction of miR156 and auxin signaling pathway is unexplored during adventitious root development.…”

“…In the Congrass1 maize mutant that overexpresses miR156, prop roots are produced at all nodes in the plant, while these roots only grow from shoot-born meristem at the juvenile nodes in wild-type plants (Chuck et al, 2007). Similarly, tomato and tobacco plants overexpressing miR156 exhibit dense aerial roots on their stems, while none appear on the stems of wild type plants (Zhang et al, 2011; Feng et al, 2016). In contrast, Arabidopsis thaliana plants transformed with 35S:MIM156 produce significantly fewer adventitious roots from the base of the hypocotyl than wild-type plants (Xu et al, 2016).…”

“…Elevated levels of miR156 promote adventitious root formation in maize, tomato, and tobacco, indicating that SPL proteins inhibit adventitious root formation (Chuck et al, 2007; Zhang et al, 2011; Feng et al, 2016). EgSPL2 and EgSPL5 are up-regulated in mature cuttings compared to juvenile cuttings of E. grandis , and the juvenile cuttings exhibited a higher adventitious rooting percentage (Abu-Abied et al, 2012).…”