Histochemical <i>ProAtUSPL1::GUS</i> activity in transgenic Arabidopsis plants.

<p>The <i>AtUSPL1</i> promoter activity was determined by histochemical localisation of GUS activity derived from the transgenic <i>ProATUSPL1::GUS</i> reporter gene. Activity indicated by blue colour can be seen in A) seedling; B) in funiculus of mature seeds; C) in flowers and stems; and D) in roots.</p

Top differential expressed genes in A) <i>rd22-1</i> and B) <i>uspl1</i> at standard growth conditions in the aerial part of 2 week old seedlings.

<p>Complete list of differential expressed genes in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110065#pone.0110065.s011" target="_blank">Table S4</a>.</p><p>Top differential expressed genes in A) <i>rd22-1</i> and B) <i>uspl1</i> at standard growth conditions in the aerial part of 2 week old seedlings.</p

AtRD22 and AtUSPL1, Members of the Plant-Specific BURP Domain Family Involved in <i>Arabidopsis thaliana</i> Drought Tolerance

<div><p>Crop plants are regularly challenged by a range of environmental stresses which typically retard their growth and ultimately compromise economic yield. The stress response involves the reprogramming of approximately 4% of the transcriptome. Here, the behavior of <i>AtRD22</i> and <i>AtUSPL1</i>, both members of the <i>Arabidopsis thaliana</i> BURP (BNM2, USP, RD22 and polygalacturonase isozyme) domain-containing gene family, has been characterized. Both genes are up-regulated as part of the abscisic acid (ABA) mediated moisture stress response. While <i>AtRD22</i> transcript was largely restricted to the leaf, that of <i>AtUSPL1</i> was more prevalent in the root. As the loss of function of either gene increased the plant's moisture stress tolerance, the implication was that their products act to suppress the drought stress response. In addition to the known involvement of AtUSPL1 in seed development, a further role in stress tolerance was demonstrated. Based on transcriptomic data and phenotype we concluded that the enhanced moisture stress tolerance of the two loss-of-function mutants is a consequence of an enhanced basal defense response.</p></div

Differential expressed genes in A) <i>rd22-1</i> and B) <i>uspl1</i> on medium containing 150mM NaCl in the aerial part of 2 week old seedlings.

<p>Differential expressed genes in A) <i>rd22-1</i> and B) <i>uspl1</i> on medium containing 150mM NaCl in the aerial part of 2 week old seedlings.</p

Influence of drought stress treatment on single and double loss of function mutants.

<p>A) Four weeks old wild type (Col-0), single and double mutant plants (<i>rd22-1</i> and <i>uspl1, rd22-1/uspl1</i>) were drought stressed for 1–5 days before they were returned to climate chamber conditions. Time of stress treatment in days is indicated left. B) Growth rates of plants under control and drought stress conditions. Bars indicate the growth rates at 22 days after sowing (DAS) for early phase of drought stress and 34 for the late phase of drought stress. For application of drought stress stop of watering started at 21 DAS. Wild type (Col-0): green bar; <i>rd22-1</i>: bright blue bar; <i>rd22-2</i>: dark blue bar; <i>uspl1</i>: purple bar; <i>rd22-1/uspl1</i>pink bar. Original data: <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110065#pone.0110065.s005" target="_blank">Figure S5 B</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110065#pone.0110065.s009" target="_blank">Table S2</a>, Asterisks indicate significant differences (p<0.01). C) NIR reflection as a water content-related parameter. Bars indicate the NIR intensity at 21 days after sowing (DAS) for start of experiment and at 35 DAS for the end of experiment. Wild type (Col-0): green bar; <i>rd22-1</i>: bright blue bar; <i>rd22-2</i>: dark blue bar; <i>uspl1</i>: purple bar; <i>rd22-1/uspl1</i>pink bar. N_control = 5, N_stress = 10 plants. Original data in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110065#pone.0110065.s010" target="_blank">Table S3</a>.</p

<i>AtRD22</i> and <i>AtUSPL1</i>, members of the BURP gene family.

<p>A. Scheme of BURP-domain containing proteins AtRD22 and AtUSPL1. BURP (named after <u>B</u>NM2, <u>U</u>SP, <u>R</u>D22 and <u>P</u>olygalacturonase isozyme) proteins are identified by their C-terminal BURP-domain (red). The BURP domains contain 4 CH-repeats (black). In comparison to AtUSPL1, AtRD22 contains an additional motif, the TXV repeats (yellow), in AtUSPL1 no repetitive domain structure can be found. AGI ID is given in brackets. Position of T-DNA insertions for the used loss-of function mutants is indicated by a green arrow. B. Quantification of <i>AtRD22</i> and <i>AtUSPL1</i> mRNA in leaves and roots. The bar diagram indicates the amplification of <i>AtRD22</i> (left) and <i>AtUSPL1</i> mRNA relative to <i>ACT2</i> mRNA (amp. rel. to <i>ACT2</i> mRNA). Leaf (green) and root (brown) tissue of well watered and drought stressed (2% RWC) plants (N = 5) was analyzed. Asterisks indicate significant differences (T-test: *** p<0.01, ** = p<0.05).</p

Chlorophyll and pheophytin content in single and double <i>BURP</i> mutants.

<p>The bars represent the total A) chlorophyll and B) pheophytin content in leaves from wild type (Col-0, green bar), single and double mutant plants (<i>rd22-1</i>, red bar, <i>uspl1,</i> blue bar and <i>rd22-1/uspl1</i>, grey bar). Chlorophyll a and b was determined separately (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110065#pone.0110065.s006" target="_blank">Figure S6A</a>) and subsumed as total chlorophyll content. Error bar represents standard error. N = 5–6 plants in duplicate. Statistical analysis was performed by oneway ANOVA at alpa  = 0.05 Tukey post hoc test: same letters indicate no difference, different letters indicate significant difference. C) The bars show the total chlorophyll content [%] relative to unstressed control plants.</p