1. Induction of salt tolerance and plant growth promotion in Arabidopsis thaliana by an endophytic Bacillus oryzicola YC7007
Mohammad Rokibuzzaman, Ajmal Khan, Md. Harun-Or-Rashid, Mohammad T. Hossain and Young Ryun Chung
Division of applied Life Sciences (BK21+), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju , Korea
ABSTRACT A
100 mM NaCl
0 mM NaCl
YC7007
Control B
lateral roots number
Control
YC7007
The salinity of soil is one of the major stresses affecting the plant health and yield negatively. The use of an endophytic Bacillus oryzicola (YC7007) with plant growth promoting activity was attempted to cope with this environmental stress. The endophytic strain YC7007 isolated previously from the roots of rice was investigated to know whether it induces resistance against high salinity in a model plant Arabidopsis thaliana. The Arabidopsis seedlings bacterized with YC7007 at different salt concentrations were shown to increase the fresh weight in I-plates upto 80 mM NaCl without physical contact. In addition, even at 100 mM NaCl, inoculation of YC7007 at a distance of 5 cm increased the number of lateral roots and fresh weight of Arabidopsis seedlings. The chlorophyll content in the bacterized seedlings was also increased as compared to the control. To confirm the effect of YC7007 inoculation on the induction of salt tolerance, the SOS (salt overly sensitive) pathway mutants, sos1, sos2 and sos3 were examined on MS agar media at 30 mM NaCl. The strain YC7007 maintains its activity in sos2 and sos3, but failed to promote the growth in sos1. Our results indicate that the inoculation of YC7007 can promote the Arabidopsis growth directly or indirectly through elimination of excess of Na+ under the saline condition. C
Fresh weight (mg/plate)
OBJECTIVES D
To evaluate the efficiency of Bacillus oryzicola YC7007 for growth promotion and salt tolerance in Arabidopsis thaliana
To investigate the biomass production, lateral roots number and primary root length mediated by Bacillus oryzicola YC7007
To estimated the chlorophyll content at different salt concentration by inoculation of an endophytic Bacillus oryzicola YC7007 .
Primary root L.(cm)
Fig. 3 Effect of YC7007 on LR formation in Arabidopsis Col-0 seedlings in salt stress. A, Representative picture of Arabidopsis after 8 days of growth in NaCl Supplemented media. Suspension of YC7007 (50 µl) was streak on the plate and 10 mM MgSO4 was used as control on NaCl containing plates. B, lateral roots number/plant C, Fresh weight D, Primary root length /plant.
MATERIALS AND METHODS
Bacterial suspension culture
Plant growth and measurement
Measurement of chlorophyll content
Affect of YC7007 on salt mutants sos1, sos2 and sos3
NaCl concentration (mM)
Chlorophyll content (mg/plate)
Control
YC7007
RESULTS A
YC7007
NaCl (mM)
Control B C
Dry weight (mg/plate)
Control
YC7007
Fresh weight (mg/plate)
NaCl concentration (mM)
Fig. 4 Effect of YC7007 bacterization on total Chlorophyll content of the dicot model plant Arabidopsis under different concentrations of NaCl. A
Colgl
sos1
sos2
sos3
Control
NaCl concentration (mM)
Fig. 1 Effect of YC7007 bacterization on the tolerance of salt stress in Arabidopsis thaliana. A, Phenotypical distinct pictorial views on the different conc. (mM) of NaCl in the I-plate. Suspension of YC7007 (50 µl) was dropped in the opposite divider I-shaped plate and 10 mM MgSO4 was used as control on NaCl containing plates. B, Fresh weight and C, Dry weight expressed in mg/plate. Every plate contains 10 plants.
YC7007
Fresh wt (mg/plate)
0 mM
0 mM B A
Control
YC7007
NaCl concentration 30 mM a b c
Root weight (mg/plate)
Colgl sos sos sos3 a b c d
Shoot weight (mg/plate)
Colgl sos sos sos3 B C
Control
YC7007
Fresh wt (mg/plate)
Control YC7007
100 mM
100 mM C c
Fig. 5 Effect of YC7007 on Salt mutant in 30 mM NaCl Concentration
REFERENCE
Han QQ, Lü XP, Bai JP, Qiao Y, Paré PW, Wang SM, Zhang JL, Wu YN, Pang XP, Xu WB, Wang ZL (2014) Beneficial soil bacterium Bacillus subtilis (GB03) augments salt tolerance of white clover. Front. Plant Science. 5:1-8.
Zhang H, Kim MS, Sun Y, Dowd SE, Shi H, Paré PW (2008) Soil bacteria confer plant salt tolerance by tissue-specific regulation of the sodium transporter HKT1. Mol. Plant Microbe Interact. 21:
Fig. 2 Arabidopsis growth in response to the strain YC7007. The plate assay was conducted in the petri plate (I-plate) kept in the growth chamber in horizontal direction. After 14 days of bacterial treatment, the fresh weight was determined. A, Representative picture B & C, fresh weight. Data represent mean values ± SE of three replicates