Figure legends
Figure 1. More UCB1 seedlings exhibited high tolerance
phenotype compared to P. integerrima
(a) Representative high and low salinity tolerance phenotypes for the
paternal genotype P. integerrima and hybrid line UCB1 after one
week 100 mM NaCl treatment.
(b) Percentage of individuals in each genotype showing high, moderate,
or low tolerance phenotypes. N=15 for P. integerrima , 22 for
UCB1.
Figure 2. Short term salt treatment did not significantly
reduce the growth of UCB1 or P. integerrima .
(a) Quantification of fresh weight after one week salt treatment showed
that UCB1 seedlings were comparable in fresh weight to P.
integerrima , and neither showed significant decreases with salt
treatment in either total or tissue specific weight (NS, two-way ANOVA,
N=7-9 plants per treatment per genotype).
(b) UCB1 exhibited a significantly higher number of lateral roots (LRs)
per plant compared to P. integerrima (P<0.05 between
genotypes, two-way ANOVA). This difference was increased after salt
treatment (P<0.01 between treatment, two-way ANOVA, P=0.01,
Tukey’s HSD, N=16-17 per treatment per genotype). Error bars = SEM.
Figure 3. UCB1 showed increased vacuolar sodium sequestration
compared to P. integerrima .
(a) UCB1 and P. integerrima root tip section stained for
Na+ showed increased number of vacuoles in UCB1
(indicated by arrowheads) after salt treatment and accumulation of
Na+ at the exodermis and endodermis (3D construction
was shown for zone 1 salt treated UCB1 to better illustrate
Na+ vacuole localization).
(b) Diagram of root tip zones staged by xylem development. z0 = zone 0,
z1 = zone 1, z2 = zone 2.
(c) Quantification of average number of vacuoles per cross section.
(P<0.01 between genotype, P<0.05 between treatment,
two-way ANOVA; * P=0.05 Tukey’s HSD.) (d) Quantification of average
number of Na+ vacuoles staged by xylem development
showed the highest vacuole count in zone 1 (NS, two-way ANOVA, N=15-51
sections/zone/genotype from 3-5 plants). Error bars = SEM.
Figure 4. Sodium staining in UCB1 showed co-localization with a
vacuolar marker.
(a-c) Co-staining of Na+ with CoroNa green (a) and
SNARF-1 for vacuole (b) showed co-localization in the vacuoles of
salt-treated UCB1 root cross section (c, indicated by arrow). CoroNa
Green staining alone (d-f), or SNARF-1 alone (g-i) do not show vacuolar
co-localization.
Figure 5. UCB1 showed higher suberin deposition than P.
integerrima in control and salt treated plants.
(a) Cross sections of root tips in both UCB1 and P. integerrimashowed increased suberization at exodermis (white arrow) and endodermis
(red arrow) when stained with Fluorol Yellow 088. (b) Quantification of
suberin fluorescence intensity (a. u.) across cross sections indicated
increase in suberization in response to salt treatment in both exodermis
and endodermis of P. integerrima and in endodermis of UCB1.
(c-d) Quantification of suberin fluorescence in zones staged by xylem
development showed a peak in suberin increase after salt treatment in
zone 1 of P. integerrima exodermis. In UCB1 both zone 0 and zone
1 showed an increase, with the greatest change occurring in endodermis
of zone 0.
(e-f) UCB1 showed consistently higher suberization than P.
integerrima in the exodermis of untreated plants for all zones, and
higher suberization in zone 0 of endodermis. After salt treatment, UCB1
showed higher suberization than P. integerrima for all zones in
both exodermis and endodermis.
(g) Salt treatment increased the percentage of suberized cells in the
endodermis of P. integerrima and in both the exodermis and
endodermis of UCB1 (* P<0.05, ** P<0.01, unpaired
2-tailed t-test) (N= 28-62 sections collected from 3-5 plants for B, G.
N=3-28 sections per zone per genotype per treatment for C-F). Error bars
= SEM.
Figure 6 . Model of UCB1 and P. integerrima root tip
response to short-term salt treatment.
Under salinity stress, UCB1 plants were able to sequester excess
Na+ in the vacuoles of cortical parenchyma of the root
tips in contrast to P. integerrima. Under control conditions UCB1
deposited more suberin in cellular barriers. In addition, while both
UCB1 and P. integerrima showed increased suberization of
endodermis and exodermis in response to salt treatment, UCB1 showed
higher suberization than P. integerrima.