Rearrangement of the Cellulose-Enriched Cell Wall in Flax Phloem Fibers over the Course of the Gravitropic Reaction

Nadezda Ibragimova,Marina Ageeva,Polina Mikshina,Oleg Gurjanov,Natalia Mokshina

doi:10.3390/ijms21155322

Nadezda Ibragimova, Marina Ageeva + Show 3 more

Open Access

https://doi.org/10.3390/ijms21155322

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Abstract

The plant cell wall is a complex structure consisting of a polysaccharide network. The rearrangements of the cell wall during the various physiological reactions of plants, however, are still not fully characterized. Profound changes in cell wall organization are detected by microscopy in the phloem fibers of flax (Linum usitatissimum) during the restoration of the vertical position of the inclined stems. To characterize the underlying biochemical and structural changes in the major cell wall polysaccharides, we compared the fiber cell walls of non-inclined and gravistimulated plants by focusing mainly on differences in non-cellulosic polysaccharides and the fine cellulose structure. Biochemical analysis revealed a slight increase in the content of pectins in the fiber cell walls of gravistimulated plants as well as an increase in accessibility for labeling non-cellulosic polysaccharides. The presence of galactosylated xyloglucan in the gelatinous cell wall layer of flax fibers was demonstrated, and its labeling was more pronounced in the gravistimulated plants. Using solid state NMR, an increase in the crystallinity of the cellulose in gravistimulated plants, along with a decrease in cellulose mobility, was demonstrated. Thus, gravistimulation may affect the rearrangement of the cell wall, which can enable restoration in a vertical position of the plant stem.

Highlights

It is well-known that higher plants, as a rule, are unable to move their whole bodies
(2) In fibers of the gravistimulated plants, epitopes of the LM5 antibody specific for β-(1,4)-d-galactan were localized in a wider cell wall layer compared to the control plants (Figure 3B,C), and the epitope of JIM7 specific for high methyl-esterified homogalacturonan was more abundant in the outer cell wall layer in fibers of the gravistimulated plants compared to the control plants (Figure 4N–Q)
We suggest that the implementation of the graviresponse is associated with the structural rearrangement of the cell walls in the flax fibers located on the pulling side of the stem

Summary

Introduction

It is well-known that higher plants, as a rule, are unable to move their whole bodies. Movements of their organ parts are possible. These movements are determined by the sensitivity of the plant to external stimuli and are provided by different types of tropisms [1,2]. In the case of gravitropism, the external stimulus that causes a motor reaction is gravity [1,2,3,4]. Despite the long-term studies of this phenomenon, there are many more questions than answers regarding the mechanisms implemented in the course of all three phases including the motor reaction [4,6]

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