UV radiation reduces epidermal cell expansion inArabidopsis thalianaleaves without altering cellular microtubule organization

Abstract

Upon chronic UV treatment pavement cell expansion in Arabidopsis leaves is reduced, implying alterations in symplastic and apoplastic properties of the epidermal cells. In this study, the effect of UV radiation on microtubule patterning is analysed, as microtubules are thought to serve as guiding rails for the cellulose synthase complexes depositing cellulose microfibrils. Together with hemicelluloses, these microfibrils are regarded as the load-bearing components of the cell wall. Leaves of transgenic plants with fluorescently tagged microtubules (GFP-TUA6) were as responsive to UV as wild type plants. Despite the UV-induced reduction in cell elongation, confocal microscopy revealed that cellular microtubule arrangements were seemingly not affected by the UV treatments. This indicates an unaltered deposition of cellulose microfibrils in the presence of UV radiation. Therefore, we surmise that the reduction in cell expansion in UV-treated leaves is most probably due to changes in cell wall loosening and/or turgor pressure.Photosynthetic functions such as solar light capture and carbon fixation are highly evolved features of plant leaves. To fulfil these functions in an optimal way, leaf development needs to be tuned to environmental conditions. Leaves are continuously exposed and subjected to environmental influences, which serve as co-regulators of leaf and plant development.

Re‐interpreting plant morphological responses to UV‐B radiation

“…Indeed, alterations in microtubuli organization are not evident under low chronic UV‐B levels (Jacques et al . ). Thus, factors associated with SIMR, such as ROS and NO, appear to mostly play a role under stress‐inducing UV‐B conditions.…”

Nitric Oxide and UV-B Radiation

“…Exactly, the recent findings of Jacques et al (2011) suggest that despite the reduction of Arabidopsis leaf epidermal cells elongation induced by chronic UV-B doses (0.1646 W m −2 ), microtubule arrangements remained unaffected because of unaltered deposition of cellulose microfibrils.…”

“…It is assumed that tubulin and actin as UV-B targets in vitro are UV-B downstream effectors able to percept amplify and/or transduce UV-B signal per NO-mediated pathways . Microtubules and actin filaments reorganization is supposed to be one of the mechanisms of UV-B-induced plant morphological responses (Staxèn et al 1993;Guo et al 2010;Chen et al 2011), however, in dose-dependent manner (Staxèn and Bornman 1994;Jacques et al 2011;Krasylenko et al 2012).…”

Plant microtubules reorganization under the indirect UV-B exposure and during UV-B-induced programmed cell death

“…1I, panel A-A") organized in radial network by MTs reorganization in adaxial leaf surface epidermal cells, 25,27 we suppose that MTs could be a good candidate for UV-Bsignal perception and its further transduction. However, their exact position in UV-B-related signaling cascades remains to be elucidated.…”

“…18,19 Cytoskeleton role in such UV-induced morphological changes as their driving force remains poorly investigated, since only a few articles are focused on the cytoskeleton reorganization in vitro as one of the events underlying UV-B-induced responses of plant cell. [21][22][23][24][25] It was shown recently that the interphase and mitotic MTs in epidermal and cortex cells of all primary root zones of Arabidopsis thaliana L. seedlings expressing gfp-map4 (microtubule-assosiated protein 4) were randomized, depolymerized and/or stabilized in dose-dependent manner after the UV-B exposure (13.6-68 kJ/m 2 ) in vivo that was accompanied by the cell swelling and excessive root hairs formation. 26 Our further experiments give additional evidences that plant MTs are involved in signal transduction under UV-B stress.…”