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. 2024 Dec 31;19(1):2348917.
doi: 10.1080/15592324.2024.2348917. Epub 2024 May 5.

Investigation of Arabidopsis root skototropism with different distance settings

Xingyu Yan  1 , Yongshun Liang  1 , Felipe Yamashita  1 , František Baluška  1
Affiliations

Investigation of Arabidopsis root skototropism with different distance settings

Xingyu Yan et al. Plant Signal Behav. .

Abstract

Plants can activate protective and defense mechanisms under biotic and abiotic stresses. Their roots naturally grow in the soil, but when they encounter sunlight in the top-soil layers, they may move away from the light source to seek darkness. Here we investigate the skototropic behavior of roots, which promotes their fitness and survival. Glutamate-like receptors (GLRs) of plants play roles in sensing and responding to signals, but their role in root skototropism is not yet understood. Light-induced tropisms are known to be affected by auxin distribution, mainly determined by auxin efflux proteins (PIN proteins) at the root tip. However, the role of PIN proteins in root skototropism has not been investigated yet. To better understand root skototropism and its connection to the distance between roots and light, we established five distance settings between seedlings and darkness to investigate the variations in root bending tendencies. We compared differences in root skototropic behavior across different expression lines of Arabidopsis thaliana seedlings (atglr3.7 ko, AtGLR3.7 OE, and pin2 knockout) to comprehend their functions. Our research shows that as the distance between roots and darkness increases, the root's positive skototropism noticeably weakens. Our findings highlight the involvement of GLR3.7 and PIN2 in root skototropism.

Keywords: Abiotic stress; PIN proteins; glutamate-like receptor; light conditions; root tropism.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Experimental setup in this study. Examples of different shade approaches we adopted: (a) treatment of small round Petri dishes (92 × 16 mm) within black boxes with a light source at the growth chamber ceiling. (b) Treatment of large square Petri dishes darkened with black covers with a light source at the growth chamber ceiling. Based on the sizes of the petri dishes, three rows of Arabidopsis seedlings were positioned in a and five rows in B, respectively. Each column was spaced 1 cm (10 mm) apart from each other as the label. To ensure consistent positioning, the inner row of seedlings was aligned with the border of the covers.
Figure 2.
Figure 2.
Skototropic response of Arabidopsis roots after 96 h growth within small round dishes inserted into the black box. Four lines of Arabidopsis seedlings were adopted: (a) Arabidopsis thaliana (col-0), (b) AtGLR3.7 knockout line (atglr3.7 ko), (c) AtGLR3.7 over-expression line (AtGLR3.7 OE), and (d) AtPIN2 deletion line (pin2 knockout). The circle contains the total number of Arabidopsis seedlings used in the experiment at the following distance settings: 0, 10, and 20 mm. The blue bars, green bars, and yellow bars, respectively, show the percentages of seedlings positively bending toward darkness, seedlings with no discernible bending trend, and seedlings bending away from darkness.
Figure 3.
Figure 3.
Skototropic response of Arabidopsis roots after 96 h growth with small round dishes darkened with black covers. Three lines of Arabidopsis seedlings were adopted: (a) Arabidopsis thaliana (col-0), (b) AtGLR3.7 knockout line (atglr3.7 ko), and (c) AtGLR3.7 over-expression line (AtGLR3.7 OE). The circle contains the total number of Arabidopsis seedlings used in the experiment at the following distance settings: 0, 10, and 20 mm. The blue bars, green bars, and yellow bars, respectively, show the percentages of seedlings positively bending toward darkness, seedlings with no discernible bending trend, and seedlings bending away from darkness.
Figure 4.
Figure 4.
Skototropic response of Arabidopsis roots after 96 h growth with large round dishes partially covered with black covers. Three lines of Arabidopsis seedlings were adopted: (a) Arabidopsis thaliana (col-0), (b) AtGLR3.7 knockout line (atglr3.7 ko), and (c) AtGLR3.7 over-expression line (AtGLR3.7 OE). The circle contains the total number of Arabidopsis seedlings used in the experiment at the following distance settings: 0, 10, 20, 30, and 40 mm. The blue bars, green bars, and yellow bars, respectively, show the percentages of seedlings positively bending toward darkness, seedlings with no discernible bending trend, and seedlings bending away from darkness.
Figure 5.
Figure 5.
Skototropic response of Arabidopsis roots after 96 h growth with square dishes partially covered with black covers. Three lines of Arabidopsis seedlings were adopted: (a) Arabidopsis thaliana (col-0), (b) AtGLR3.7 knockout line (atglr3.7 ko), and (c) AtGLR3.7 over-expression line (AtGLR3.7 OE). The circle contains the total number of Arabidopsis seedlings used in the experiment at the following distance settings: 0, 10, 20, 30, and 40 mm. The blue bars, green bars, and yellow bars, respectively, show the percentages of seedlings positively bending toward darkness, seedlings with no discernible bending trend, and seedlings bending away from darkness.
Figure 6.
Figure 6.
Comparative perception of darkness in Arabidopsis and human being. The Arabidopsis thaliana seedling (about 100 μm in diameter) positioned at 20 mm from darkness is equivalent to a person with a diameter of 0.7 m being situated 140 m away from darkness.
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