Cytokinin application to the shoot apical meristem of Sinapis alba enhances secondary plasmodesmata formation

Abstract

A single application of cytokinin benzyladenine causes a threefold increase in the frequency of plasmodesmata in the vegetative shoot apical meristem (SAM) of Sinapis alba plants. This increase is observed 20 h after application within all cell layers (L1, L2, L3) as well as at the interfaces between these layers. Evidence is presented indicating that cytokinin promotes mainly the formation of new secondary plasmodesmata. A similar increase in the frequency of secondary plasmodesmata was observed in the Sinapis SAM during the floral transition induced by a single long day, suggesting that this effect of the long day is mediated by cytokinin.

Salicylic Acid Regulates Plasmodesmata Closure during Innate Immune Responses in Arabidopsis

“…Rather, they undergo various types of structural modifications and degeneration/regeneration processes to meet the specific needs of cells that may set out rapid expansion, different developmental phases or differentiation, or adaption processes in response to the changes in various physiological and environmental conditions (Ehlers and Kollmann, 2001;Roberts and Oparka, 2003;Lucas and Lee, 2004;Burch-Smith et al, 2011;Burch-Smith and Zambryski, 2012). For instance, PD frequency and density change as cells grow and develop (Gunning, 1978;Seagull, 1983;Ehlers and Kollmann, 1996;Burch-Smith and Zambryski, 2010;Ehlers and van Bel, 2010) or during shifts from vegetative to reproductive phases (Ormenese et al, 2000;Ormenese et al, 2002;Ormenese et al, 2006); PDs differentiate from simple to complex forms (Faulkner et al, 2008;Fitzgibbon et al, 2013); PDs are completely disintegrated during guard cell maturation (Wille and Lucas, 1984); PD permeability undergoes temporal regulation by environmental conditions, such as daylength and temperature (Ormenese et al, 2006;Bilska and Sowinski, 2010;Rinne et al, 2011), etc. Permeability, dilation, or structure of PDs can be also altered during infection by microbial pathogens (Heinlein, 2002;BenitezAlfonso et al, 2010;Schoelz et al, 2011;Ueki and Citovsky, 2011).…”

Peeking into Pit Fields: A Multiple Twinning Model of Secondary Plasmodesmata Formation in Tobacco

“…The absence of the ISE2 protein (a DEVH-box RNA helicase) affects a critical factor required for correct PD development. In addition, the formation of secondary PD is enhanced in meristems by the addition of the hormone cytokinin (Ormenese et al, 2006) and is arrested in plants overexpressing an apoplastic yeast acid invertase (Ding et al, 1993). It seems likely that the extending cell wall might respond to a number of extracellular cues, such as radial stretching forces that feed back on secondary PD formation.…”

Evidence for Unidirectional Flow through Plasmodesmata

“…Although the size exclusion limit of the PD pore was originally thought to be relatively constant (Erwee and Goodwin, 1983;Terry and Robards, 1987), it is now clear that "not all PD are equal," in the sense that the size exclusion limit (SEL) of the pore may differ substantially during cell development (Duckett et al, 1994;Crawford and Zambryski, 2000;Ruan et al, 2001) in response to environmental conditions (Epel and Erlanger, 1991;Cleland et al, 1994;Schulz, 1995) and the location of a given cell-cell interface in the plant Goodwin, 1983, 1985;Duckett et al, 1994;Ruan et al, 2001). It is also established that the SEL of the pore may respond to intracellular cues such as water relations (Oparka and Prior, 1992;Schulz, 1995), metabolic status (Tucker, 1993;Cleland et al, 1994;Wright and Oparka, 1997), cytosolic Ca 2+ levels (Tucker, 1988;Tucker and Boss, 1996;Holdaway-Clarke et al, 2000), and hormones (Ormenese et al, 2006). The picture emerging is one in which the PD pore functions as a dynamic structure that alters its SEL in response to changing local conditions (Maule, 2008).…”