boron transport in plants:boron transport in plantsboron transport in plants:boron transport in...
Post on 18-Jan-2021
8 Views
Preview:
TRANSCRIPT
Boron transport in plants:Boron transport in plants:coordinated regulationcoordinated regulation
of transporters
Kyoko Miwa, Toru FujiwaraBiotechnology Research Center,
The University of Tokyo
Boron (B) is essential for plantsIntroduction1
B deficiency symptoms Cross-linking of RG-II in cell wall
Boron (B) is essential for plants
B deficiency symptoms Cross linking of RG II in cell wall
Watanabe (1985) Kobayashi et al.(1996),O’Neill et al.(20
Occurrence of B deficiency was reported in 80 countries and 132 crop species(Shorrocks, 1997)
High concentration of B is toxicIntroduction2
High concentration of B is toxic.B toxicity symptoms
(Watanabe,1985)
Plants need to control B concentration in optimum range.Presentation by Sakamoto, 30th, 3:00pm
Boron transporters?Introduction3
・B(OH)3 + H2O → B(OH)4- + H +
(pKa = 9.25, 25 °C )(p , )
Boron is transported passively along transpiration streamBoron is transported passively along transpiration stream.
B
(Marschner 1995)
B homeostasis by regulation of B transporters
Low B High B
(2)Preferential distribution of B into
ti b NIP6 1(3)Exclusion of
toxic B by BOR4
young portions by NIP6;1
(1)Efficient uptake and l l di f Bxylem loading of B
by NIP5;1 and BOR1
Arabidopsis thaliana bor1-1 is d f ti i l l di f bdefective in xylem loading of boron.
100 WTbor1-1
WTbor1-1
100
Root cell sap Xylem exudate
µM µM
60
80bor1-1bor1-1
60
80
20
40
20
40
Tracer B in media (µM)
00 20 40 60 80 100
00 20 40 60 80 100
Tracer B in media (µM)
(Noguchi et al., 1997, Takano et al., 2002 Nature)
BOR1 B ra
tion
DW
)
567 vector
concentrates B into xylem under B
con
cen
trol
B/
kg D
345
BOR1ylow B supply.
(Xylem loading) Cel
lula
r B
(m
mo
12
(Xylem loading)
X l
C
0
CortexPericycleXylem
parenchyma
Casparian stripEpidermisMedia
Endodermis
XylemBOR1
2
(Takano et al., 2002, Nature)
BOR1 accumulation is regulated at post transcriptional level
The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
at post-transcriptional level.Protein
mRNAroot
rootroot
BOR1PBOR1
-B +B
BOR1
GFPBOR1P35S BOR1-GFP
+B 0 min
+B 30 min
Subcellularlocalization
+B 120 min
-B 120 min
+B 60 min
(Takano et al., 2005, PNAS)
Stele
B transport model by BOR1
Cortex
Stele
Pericycle Xylemparenchyma
Casparian stripEpidermisMedia
EndodermisHigh B
Xylem
BOR1
Low B
XylemBOR1
BOR1Xylem-directed export of B by BOR1
NIP5;1 is upregulated by low B NIP5;1 mRNA level in roots
-B 24h--> +B 24h B 24h
(Takano et al. 2006Plant Cell)
NIP5;1 is important for efficient B uptake in roots under low BB uptake in roots under low B.
(Takano et al. Plant Cell 2006)
Stele
B transport model in Arabidopsis
Cortex
Stele
Pericycle Xylemparenchyma
Casparian stripEpidermisMedia
EndodermisHigh B
Xylem
XylemBOR1
Low BNIP5;1
NIP5;1
yNIP5;1
Transcriptional regulation
post-transcriptional regulation
Coordinated expression of transporters and channelstransporters and channels
From Soils Toward XylemFrom Soils Toward Xylem
NIP5;1 BOR1 BBB
Channels facilitate influx
Transporters export out f th ll i tfacilitate influx
into cellsof the cells against
concentration gradient
NIP6;1 preferentially distributes B into young leaves under limited Binto young leaves under limited B.
- BB
+B
(Tanaka et al. 2008 Plant Cell)
A Rice BOR1 ortholog also
OsBOR1 (XII)
functions in B transportosbor1-2osbor1-13830 bp (2137 bp)
100 bp
OsBOR1 (XII)LB
osbor1 2LB
osbor1 13830 bp (2137 bp)
; exon ; intron ; Tos17 ; primer
WT
osbor110 cm
- Bosbor1
(Nakagawa et al.,2007 Plant Cell)
Presence of efflux B transporter for B tolerance was predicted in barleyB tolerance was predicted in barley.
+B ++BRoot B concentration
Sensitive cultivar
Tolerant cultivar
B in media (mM)SensitiveSensitive
(Hayes et al., 2004)Tolerant
(Sutton et al., 2007)
Tolerant
Which is for B tolerance among six BORs in Arabidopsis?
Required for growth
among six BORs in Arabidopsis?
BOR1BOR2BOR3
q gunder B limitation
BOR4BOR7
S ifi ll
0.05
O
BOR5BOR6
Specificallyexpressed in pollen
BOR4-GFP was not decreased hi h B lupon high B supply.
GFPBOR4Pro35S
line4-B +B ++B120
(kDa)B +B ++B
Root120
BOR4-GFP100
8080
(Miwa et al., 2007 Science)
B concentrations were decreased i BOR4 i liin BOR4 expressing lines.
80
100WT
60
80at
ion
gDW
)++ B(3 mM)
40
once
ntra
mol
B/k
g
WTBOR4line
(3 mM)
0
20
B c
o(
m BOR4line
0Roots Shoots
(Miwa et al., 2007)
BOR4 is localized to distal side of l b f t id iplasma membrane of root epidermis.
GFPBOR4genomeProBOR4
(Miwa et al., 2007)
Overexpression of BOR1 improved l t th d B li it tiplant growth under B limitation
GFPBOR1P35S 0.5 µMB
L15L10Wild type BOR1 overexpressor
BOR1 over Wild type -expressor
L10(Miwa et al., 2006, Plant J)
Enhanced expression of NIP5;1improved root growthimproved root growth
Wild type NIP5;1AC/ NIP5;1AC/35S-BOR1P35S ProNIP5;1 NIP5;1P35S ProNIP5;1 NIP5;1
Wild type NIP5;1AC/35S-BOR1
NIP5;1AC/35S-BOR1
35S BOR1
Grown on -B media for 23 daysBar : 5 cm
(Kato et al., 2009)(Line 1) (Line 6)
Overexpression of BOR4 conferred high B toleranceconferred high B tolerance.
Wild type BOR4 overexpressing ArabidopsisGFPBOR4Pro35S
Wild type BOR4 overexpressing Arabidopsis
++BToxic level B
10 mM
(Miwa et al., 2007,Science) Line 5 Line 4 Line 12
B homeostasis by regulation of B transporters
Low B High B
(2)Preferential distribution of B into
ti b NIP6 1(3)Exclusion of
toxic B by BOR4
young portions by NIP6;1
(1)Efficient uptake and l l di f Bxylem loading of B
by NIP5;1 and BOR1
ConclusionConclusion
• Plants regulate B transportPlants regulate B transport.• Expressions of B transporters are regulated
at mRNA and protein levels in response toat mRNA and protein levels in response to B conditions.P l l li ti f th t t i lik l• Polar localization of the transporters is likely to be important for directional trans-cellular t ttransport.
• B transporters are useful for improvement of B-stress tolerance.
top related