Abstract: Salt stress is a major environmental factor that inhibits crop growth.  Trichoderma spp. are the most efficient biocontrol fungi and some of the strains can stimulate plant growth.  Phosphate solubilization is known as one of the main mechanisms in promoting plant growth, but the underlying mechanisms of phosphate solubilization in the salinity still need to be explored.  The Trichoderma asperellum Q1 isolated and identified in our lab is a beneficial rhizosphere biocontrol fungus with a high phosphate solubilization activity.  It could produce acid and alkaline phosphatases when using insoluble organic phosphorus as the sole phosphorus source, the salt stress increased the phosphorus-solubilization ability of the strain and the activities of the two enzymes.  Furthermore, an acid phosphatase was purified from the fermentation broth by ammonium sulphate precipitation, ion-exchange, and gel filtration chromatography.  Its molecular weight was 55 kDa as determined by SDS-PAGE.  The purified acid phosphatase was used to investigate growth performance of Arabidopsis thaliana by plate assay and the result showed that it contributed to Arabidopsis growth by transforming organic phosphate into a soluble inorganic form under salt stress.  To our knowledge, this is the first report on acid phosphatase purification from T. asperellum and its function in regulation of plant growth under salt stress.

Key words: Trichoderma asperellum, Arabidopsis thaliana, acid phosphatase, plant-growth promotion, salt stress