Study On Colonization And Growth-promoting Molecular Mechanism Of Affinity Potassium Solubilizing Rhizosphere For Tobacco

In order to study the colonization dynamics in soil and tobacco rhizosphere,their promoting effects and molecular mechanism of potassium solubilizing rhizobacteria for tobacco,in this work,Pseudomonas sp.TK35 and TK55 with specific affinity for tobacco were selected as study materials.The colonization of the two strains in different types of soil and tobacco rhizosphere were investigated by using the lux AB gene marker technique.The effects of the two strains on the growth and development of tobacco and the expression of HPGPnt3 gene were studied.The results will provide theoretical basis and experimental data for the study of the growth promoting molecular mechanism of plant growth-promoting rhizobacteria.The plasmid p TR102::lux AB,km,tet wes extracted from E.coli WA803 strain,and the lux AB gene was introduced into TK35 and TK55 cells respectively by method of electroporation.The bacterial solution was spread on LB medium plates containing km and placed in an incubator until the colonies were formed.The labeled strains TK35-L and TK55-L with lux AB markers were screened by observing its luminescence after added capraldehyde in dark.The colonization of two strains in yellow cinnamon soil,red soil and nutrient soil was studied.The results showed that strain TK35-L and TK55-L could survive for a long time in these three kinds of sterilized soils and unsterilized soils.The number of labeled bacteria in sterilized soils was higher than that in unsterilized soil.The number of two strains showed an upward trend after adding nutrients to the unsterilized soil.Both of these two strains can survive quite a long time in different types of soil and adapt to different soil conditions.They have strong competitive abilities with indigenous microorganisms in soils.Root bag test was used to study the colonization of two strains in tobacco rhizosphere.The results showed that both of the two strains had high colonization density in all parts of tobacco roots.On the 60th day of tobacco growth,the colonization density of TK35-L and TK55-L under the root of 8cm can still reach 2.1×10⁵ CFU·g^-1 and 1.3×10⁴ CFU·g^-1,which indicated that the two strains could multiply along the growth of the root,and could survive and propagate in the tobacco rhizosphere for a long time.The effects of strains TK35-L and TK55-L on the growth of tobacco were determined.The results showed that both the two strains could increase total length,projected area,surface area,volume,tips,forks and crossings of tobacco root.At the same time,the two strains can also significantly promote tobacco root dry weight,root fresh weight,seedling dry weight and seedling fresh weight.Effects of the two affinity potassium solubilizing rhizosphere on expression levels of HPGPnt3 gene,a tobacco root development related gene,were determined by quantitative reverse-transcription PCR method.The results showed that TK35-L and TK55-L could significantly increase the expression levelof HPGPnt3 gene.Two strains could promote tobacco growth by regulating the expression of HPGPnt3 gene.