Mechanism Research Of MdBT2 Regulating Root Development And Drought Resistance In Apple

As an important cash crop,apple faces a variety of biotic and abiotic stress in their development process.Although excessive nitrogen improves fruit yield,it brings many other questions,such as decreased quality and reduced tolerance to pathogen in agricultural production.At the same time,we find that excessive nitrogen causes a bad performance in root development.Plant roots,which respond to environmental change spatiotemporally,are mainly involved in anchorage,and water and nutrient absorption.Sessile plants have evolved adaptive mechanisms in their root systems.Nitrate?NO₃^-?accounts for the majority of nitrogen taken up by plants.Additionally,nitrate can act as a signaling molecule in plant metabolism and development.The mechanism of how nitrate regulates root development in apple remains unclear.Most plants face drought stress in their growth and development:Mild drought may cause a reduction of yield as well as quality in crop and severe drought even leads to death of plant.In china,most apple trees were cultivated in hilly and mountains region where lacks nutrition substance and rain,which brings a great threat.Post-translational modification of protein is crucial to plants in quick response to environmental stimuli and regulation of protein structure,function and protein stability.Among these,ubiquitination,which facilities its target protein to degradation,is an important modification.In this study,using apple seedlings,apple calli and Arabidopsis,molecular biology method was used to study the mechanism of the regulation of Md BT2 in apple root development and drought resistance:1.Nitrate influences apple root development in an-auxin dependent manner:Low nitrate be reduced or induced in Md BT2 overexpression or Md BT2-anti lines.2.Md ARF8 and Md IAA3 was demonstrated to interact with Md BT2 using a Y2H,Pull- Md ARF8.Lateral root number of 35S::Md ARF8-GFP+35S::Md BT2 was significantly lower compared with 35S::Md ARF8-GFP.3.Md BT2 is a negative factor in the auxin signaling pathway.Based on GUS stain assays, auxin signaling was enhanced or repressed with reduction or induction of Md BT2.4.Both Md BT2 and Md NAC143 could respond to drought stress.Md BT2 and Md NAC143 drought in apple.In this study,we found that Md BT2 acted as a key regulator to respond both high nitrate and drought stress and illustrated the regulatory networks of"high nitrate-Md BT2-Md IAA3/Md ARF8-Md GH3.1/Md GH3.6"and"drought-Md BT2-Md NAC143".Md BT2 can integrate nitrate signal and auxin signaling in regulation of root development.Additionally,Md BT2 antagonistically with Md NAC143 to regulate drought response.The discovery may support some meaningful suggestion for seeking drought resistance species.Our findings may provide some theoretical significance for understanding of perennial apple and how they respond to external environmental stimuli to regulate their development.