Fig 1.
Comparison of Root Hair Length in 10-Day-Old Seedlings of WT, max1-1, and max2-1 Plants.
(A, B) Root hair length of control (0 μM) and GR24-treated (1 μM) plants. (C, D) Root hair length of WT and SL-mutants grown under low- and high-Pi conditions. Scale bar = 1 mm. Data presented in panels A and C are the means ± SD of 10 biological replicates. Two independent experiments were performed with similar results. Columns marked with ** indicate significant differences (Student’s t-test, P < 0.01). WT Columbia-0 (Col-0), max1-1, and max2-1 plants are shown as black, white, and grey-filled bars, respectively.
Fig 2.
Comparison of Anthocyanin Accumulation in WT, max1-1, and max2-1 Arabidopsis Plants.
(A, B) Anthocyanin accumulation in four-week-old plants in the absence (0 μM) or presence (5 μM) of GR24. (C-F) Anthocyanin accumulation in three-week-old SL-deficient plants grown under low- and high-Pi (C, D), and low-N (F). Scale bar = 0.2 cm. Data presented are the means ± SD of 4 biological replicates (each replicate contained ten or more plants). Two independent experiments were performed with similar results. * and ** indicate significant differences with respect to plants grown under conditions of high Pi (t-test, P < 0.05 and P < 0.01, respectively). Black, white, and grey bars depict WT, max1-1, and max2-1 plants, respectively.
Fig 3.
Effects of GR24 on Acid Phosphatase Secretion in 10-Day-Old Seedlings.
(A) Acid phosphatase activity on root surfaces as detected by treatment with 5-bromo-4-chloro-3-indolyl phosphate p-toluidine salt (BCIP). Scale bar = 5 mm. (B) Acid phosphatase activities as detected by treatment with p-nitrophenylphosphate (pNPP). Data are the means ± SD of 6 (WT and max2-1) and 5 (max1-1) replicates (each replicate contained six or more seedlings). Three independent experiments were performed with similar results. * indicates significant differences from control plants (Student’s t-test, P < 0.01).
Fig 4.
Comparison of Whole Plant Weight in WT, max1-1, and max2-1 Lines.
(A) Effect of GR24 on whole plant weight under high-Pi condition. (B) Ratio of plant weight of max1-1 and max2-1 grown under low- and high-Pi conditions. Data are the means ± SD of five biological replicates (each replicate contained six or more seedlings). Three independent experiments were performed with similar results. * indicates significant differences from control plants (A) and WT (B) (Student’s t-test, P < 0.01). Black, white, and grey bars represent WT, max1-1, and max2-1 plants, respectively.
Fig 5.
Gene Expression Analysis in WT and max1-1 Roots.
(A) Expression levels of PSI genes altered in max1-1 roots. The expression level of each transcript is displayed relative to the expression level in the WT, which was assigned a value of 1. Black and white bars indicate the results of RNA-seq analysis. Green and purple bars indicate the results of qRT-PCR. The UBC gene was used as a reference in qRT-PCR. (B) Scatterplots showing the results of two experiments, “max1 mutant (max1-1 mutants compared with WT)” and “-Pi (roots of 10-day-old plants grown on a Pi-deprived plate compared with mock treatment)”. The x and y axes indicate transcript responses as a log signal ratio (mutant or treatment/WT or mock, respectively). Gene expression response of max1-1 and Pi responsive genes were plotted. Fisher’s exact test indicates the significant correlation between “max1 mutant” and “-Pi” (P < 0.001).
Table 1.
Genes induced (UP) and repressed (DOWN) in max1-1 mutant (TOP20).
Fig 6.
Comparison of Phosphorus and Micronutrient Content in Three-Week-Old WT and max1-1 Seedlings Grown with High (1 mM) or Low (0.1 mM) Pi in the Presence or Absence of GR24.
Data represent the means ± SD of five biological replicates (each replicate contained ten or more seedlings). ** indicates significant differences from GR24 untreated plants (Student’s t-test, P < 0.01).
Fig 7.
Model illustrating how SLs impact adaptation to Pi starvation.
Upregulation of SL biosynthesis during Pi starvation can impact the ability to respond to low-Pi response through regulation of root hair elongation and PSI gene expression, though unknown SL independent pathways are involved in the adaptation of a low-Pi response.