MiR156-mediated Responses To Phosphorus Deficiency In Arabidopsis Rhizosphere Acidification

Phosphorus (P) is an essential component of all organisms. Not only is it found in ATP, nucleic acids,and membrane phospholipids, but it also plays an important role in plant growth, development,photosynthesis, enzyme reactions and signal transduction processes. Despite the total P is rich in soils, mostof the P that remained in the soil is converted to organic compounds by microorganisms or becomesinsoluble by interacting with cations. As a result, plant often face the risk of low phosphorus stress becauseP can be acquired by plants only as inorganic phosphate.Plants have evolved a series of adaptive strategies to overcome problems with P availability.Underlow P stress, plants not only increase their lateral roots, and root hair length and density explore new Piresources in the soil more efficiently, but also enhance the root secretion of organic acids, phosphatase andRNase to increase the rhizosphere acidification ability to release the P in soil. The expression level ofphosphate starvation response genes is induced to improve the phosphorus uptake capacity. Plants also canalter their own metabolic pathways to recycle phosphorus. In addition, Some miRNAs can be induced toregulate the phosphorus induced starvation genes in post-transcription level. Only understanding theplant-specific response to low phosphorus stress, tracking the specific control gene, we can develop andcultivate new varieties of crops that use the nutrient phosphorus efficiently in molecular level.In recent years, the function of plant microRNAs response to environmental stress has becomeconcerned. The function of star molecule miR399in the regulation of phosphorus homeostasis has alreadyreceived a number of significant achievements. Deep sequencing of Arabidopsis small RNAs wasconducted to reveal miR156that was differentially expressed in response to phosphate deficiency. But themechanism of miR156how to response to P deficiency is not clear.This work use miR156overexpression line (Pro35S:MIR156), in which miR156was expressed fromthe35S promoter, and the miR156target mimicry line (Pro35S:MIM156), which reduces miR156activity,to study the role of miR156response to low phosphorus stress. The root architecture of miR156overexpression line was alterd, the lateral root number and density,and the accumulation of anthocyanin content was increased, the rhizosphere acidification capacity was enhanced,the pH value in the rhizospherewas decreased to5.2±0.04. Yet the number and density of lateral roots of miR156target mimicry line wasreduced, the accumulation of anthocyanin content was decreased. The plant rhizosphere acidificationweaken. The pH value in the rhizosphere was decreased to5.43±0.03. Analysis of physiological andbiochemical result showed that miR156overexpression line increased plant cytosolic pH and H+-ATPactivity, while loss of miR156function make lower intracellular pH and H+-ATP activity. We furtherexamined the activation effect of roots secrete acids response to insoluble phosphorus. We found that thesurvival rate of miR156overexpression line increased in iron phosphate medium, yet miR156targetmimicry line can’t survive in iron phosphate medium. To study the function of miR156-Targeted SPLGenes under low P condition, some SPL expression was suppressed.The rhizosphere acidificationcapability of SPL9and SPL13overexpression line was weaker than WT. the activation of insolublephosphate effect was lower than WT. These results show that miR156participated in the rhizosphereacidification process response to phosphorus deficiency, and at least regulate its target genes SPL9, SPL13participated in this process.