SPL1 is Involved in the Regulation of Rhizosphere Acidification Reaction Under Low Phosphate Condition in Arabidopsis

doi:10.11983/CBB15080

Abstract

Abstract: Under low phosphate (Pi), the rhizosphere acidification of plants is a vital strategy to cope with low Pi stress. However, how plants perceive and transduce the low Pi signal and acidify the rhizosphere is not clear. A mutant, spl1, with decreased rhizosphere acidification induced by low Pi, was isolated from a T-DNA library by using the pH indicator (bromocresol purple). After 8 h incubation in low Pi medium containing bromocresol purple, the color of the rhizosphere of wild-type (WT) seedlings on the low Pi medium turned yellow, whereas that of the rhizosphere of spl1 seedlings did not change, which suggested decreased rhizosphere acidification capacity of spl1. The anthocyanin content was higher for spl1 than the WT with 20 days of low Pi treatment. The number and the length of root hairs of spl1 increased under normal conditions. Further research suggested that the Pi content of the spl1 mutant was slightly decreased in shoot but increased in root under Pi deficiency. Moreover, the expression of Pi transport-related genes in the spl1 mutant increased under Pi deficiency. Molecular genetics analysis revealed that the expression of SPL1 was induced by low Pi stress. SPL1 was mainly expressed in Arabidopsis leaves and flower tissues and the SPL1 protein was widely distributed in each part of the cell. These results indicate that SPL1 is involved in low Pi-induced rhizosphere acidification, regulation of multiple low Pi responses and Pi starvation-induced gene expression.

Key words: Arabidopsis, rhizosphere acidification, spl1, low Pi

Kaijian Lei, Jing Ren, Yuanyuan Zhu, Guoyong An. SPL1 is Involved in the Regulation of Rhizosphere Acidification Reaction Under Low Phosphate Condition in Arabidopsis[J]. Chinese Bulletin of Botany, 2016, 51(2): 184-193.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB15080

https://www.chinbullbotany.com/EN/Y2016/V51/I2/184

Figures/Tables 7

Figure 1 Arabidopsis thaliana spl1 mutants show the phenotype of rhizosphere acidification deficiency and decreased acidi- fication capacity (A) T-DNA insertion sites in spl1-1 and spl1-2; (B) Reverse transcriptase-PCR analysis of SPL1 expression; (C) The rhizosphere acidification reaction of WT and spl1 mutants under MS and low phosphate (LP) conditions (12.5 μmo∙L−1 H2PO4−) (Bar=1 cm); (D) The acidification capacity of WT and spl1 mutants. Asterisk represent statistically differences compared with the wild type (P<0.05).

Figure 2 The anthocyanin accumulation in Arabidopsis thaliana spl1-1 and spl1-2 under low Pi condition (A) The anthocyanin accumulation in wild type (WT), spl1-1, and spl1-2 plants during Pi sufficient and Pi deprivation; (B) Anthocyanin content was determined in WT and spl1 plants grown with normal and low Pi (LP) on the twentieth day of Pi starvation. Asterisk represents statistically differences compared with the wild type (P<0.05).

Figure 3 The Pi content analysis of Arabidopsis thaliana spl1 mutants Seven-day-old seedlings were transferred to MS or low Pi (LP) medium for 14 d and then harvested for Pi content analy- sis. Asterisk represents statistically differences compared with the wild type (P<0.05).

Figure 4 SPL1 alters root hair architecture (A) Images of root tips with intact root hair from WT, spl1-1 and spl1-2 plants (Bar=1 mm); (B), (C) Number of root hair (B) and root hair length (C) under MS and low Pi (LP) condition. *Data significantly different from the corresponding controls are indicated (P<0.05).

Figure 5 Expression analyses of the SPL1 gene (A) in Arabidopsis seedlings in response to low phosphate (LP) stress and expression pattern of Pi starvation induced genes in spl1 mutants (B)

Figure 6 Tissue-specific expression of SPL1 (A) Histochemical localization of GUS activity directed by SPL1::GUS fusions in transgenic Arabidopsis; (B) qRT-PCR showed the relative abundant of SPL1 gene in different tissues, including root, stem, leaf and flower

Figure 7 Localization of GFP signals from pHBT empty vector (A−D) and SPL1 (E−H) fused with GFP (A), (E) Fluorescence images under confocal microscopy; (B), (F) Chloroplast fluorescence; (C), (G) Bright-field images of the cells; (D), (H) Merged fluorescence. Bar=5 µm

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