| Phosphorus is necessary for plant growth and development, and takes part in many processes inplants, such as photosynthesis, respiration and transduction of signal. Phosphorus is also an importantstructural component of nucleic acids, phospholipids and high-energy phosphate compound such as ATP(Adenosine triphosphate) and ADP (adenosine diphosphate). Phosphorus also plays an important role inimproving the ability of plants to insist stress. Plants need large amount of phosphorus to maintain normalgrowth and development. Plants mainly absorb and use two forms of phosphorus, H2P04-and HP042-.Mobility of phosphorus in soil is poor, the majority has been united into insoluble complex or organicphosphorus, so phosphorus content of the soil is very low. Plants in most regions of the world are under thephosphorus deficiency stress, phosphorus deficiency has become one of the factors restrict agriculture.Through the long evolution process, plants have developed many strategies to adapt to Phosphorusstarvation, such as morphological adaptation, including increase of shoot/root, changes of root architecturesystem, etc.; physiological adaptation, including induction of high-affinity phosphate transporter, secretionof organic acid and acid phosphatases. Some genes and signals associated Phosphorus deficiency stressresponse have been reported. Although the mechanism of plants response to phosphorus deficiency stresshas been researched a lot, the specific mechanism of phosphorus absorption, utilization and transportationin plant is not clear. Rhizosphere acidification is an important mechanism of plants response to phosphorusdeficiency stress. It can activate phosphorus from insoluble complex, so the efficiency of phosphorusAbsorption in soil is improved. Although there are many reports about phosphorus deficiency induced rhizosphere acidification, but the molecular mechanism of plant percept phosphorus signal and releaseorganic acid has not been elucidated.We use the method of pH indicator bromocresol purple to screen out a rhizosphere acidificationdeficiency mutant, named p444. We quantified the rhizosphere pH of plants under low phosphoruscondition. The rhizosphere pH of WT is5.4±0.005, and that of p444is5.55±0.02, The rhizosphere pH ofp444is much higher than WT, so phosphorus deficiency induced rhizosphere acidification of p444isweaker than WT, p444gene mutation is involved in phosphorus deficiency-induced rhizosphereacidification process. Plasma membrane H+-ATPase plays an important role in phosphorusdeficiency-induced rhizosphere acidification process. Vanadate is an inhibitor of plasma membraneH+-ATPase. The acidification ability of WT is suppressed in phosphorus deficiency medium with1mMNa3VO4, the rhizosphere acidification deficiency phenotype of WT is similar to p444, so we speculate p444gene mutation may inhibit the plasma membrane H+-ATPase activity, thus affect the rhizosphereacidification. We also tested a series of phenotypes of p444under low phosphorus condition, thechlorophyll content in p444is less than WT, the PSⅡphotosynthetic rate of p444is weaker than WT, thephosphorus transport ability of p444is better than WT, the accumulation of anthocyanin in p444is less thanWT, the increase in lateral density of p444is more than that of WT. The mutation gene of p444not nolytake part in phosphorus deficiency-induced rhizosphere acidification process, but also affect the response ofplants to phosphorus deficiency process.Map-based gene cloning result show that the phenotype of p444is due to25bp bases mutation inthe coding region of gene At5g04140. At5g04140gene mutation results in premature termination of proteintranslation. We get p444M mutant (a T-DNA insertion line for At5g04140gene). Through the phenotype analysis of p444M, we get the further evidence that p444phenotype is caused by At5g04140gene mutation.In addition, we build P444::PCAMBIA1381-GUS vector, laying the foundation for the further study of thetissue localization and the relationship between gene and phosphorus. |
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