Actin-dependent fluid-phase endocytosis in inner cortex cells of maize root apices

Abstract

The fluorescent dye Lucifer Yellow (LY) is a well-known and widely-used marker for fluid-phase endocytosis. In this paper, both light and electron microscopy revealed that LY was internalized into transition zone cells of the inner cortex of intact maize root apices. The internalized LY was localized within tubulo-vesicular compartments invaginating from the plasma membrane at actomyosin-enriched pit-fields and individual plasmodesmata, as well as within adjacent small peripheral vacuoles. The internalization of LY was blocked by pretreating the roots with the F-actin depolymerizing drug latrunculin B, but not with the F-actin stabilizer jasplakinolide. F-actin enriched plasmodesmata and pit-fields of the inner cortex also contain abundant plant-specific unconventional class VIII myosin(s). In addition, 2,3 butanedione monoxime, a general inhibitor of myosin ATPases, partially inhibited the uptake of LY into cells of the inner cortex. Conversely, loss of microtubules did not inhibit fluid-phase endocytosis of LY into these cells. In conclusion, specialized actin- and myosin VIII-enriched membrane domains perform a tissue-specific form of fluid-phase endocytosis in maize root apices. The possible physiological relevance of this process is discussed.

A Comparative Study of the Involvement of 17 Arabidopsis Myosin Family Members on the Motility of Golgi and Other Organelles

“…Plant myosins have been implicated in various cellular activities, such as cytoplasmic streaming (Shimmen and Yokota, 2004;Esseling-Ozdoba et al, 2008), plasmodesmata function (Baluska et al, 2001;Volkmann et al, 2003), organelle movement (Nebenfü hr et al, 1999;Jedd and Chua, 2002), cytokinesis (Molchan et al, 2002;Collings et al, 2003;Volkmann et al, 2003), endocytosis (Volkmann et al, 2003;Baluska et al, 2004;Samaj et al, 2005), and targeted RNA transport (Hamada et al, 2003). Actomyosin mediated cytoplasmic streaming found in various algae cells reach velocities of up to 100 mm s 21 , which is the fastest known myosin-mediated movement (Shimmen and Yokota, 1994).…”

Local Turgor Pressure Reduction via Channel Clustering

“…Endocytosis in plants has some parallels to the process in yeast, in particular its polymerized-actin dependence (42,43). The difficulties of overcoming high turgor pressure in plants by an actindependent process might thus be eased by a local turgor pressure reduction mechanism like that we discuss here for yeast.…”

The mixotrophic nature of photosynthetic plants

“…Internalised lucifer yellow, an endocytosis marker, occurs in transition zone cells of the inner cortex of intact maize root apices indicating that large molecules are transported across cortex cells (Baluska et al 2004, who acknowledged that results from the use of lucifer yellow can be compromised by the occurrence of carrier-mediated movement of this tracer across plant membranes). That larger molecules enter roots via endocytosis has long been proposed as exogenously supplied macromolecules such as DNA were detected in roots (reviewed by Paungfoo-Lonhienne et al 2012).…”