Study On The Feedback Regulation Mechanism By Scion On Rootstock Potassium Uptake In Grafted Watermelon

Potassium is an essential element for plant growth and development.The agricultural soil across the world has widespread potassium deficiency.Potassium deficiency adversely influences the growth of crops,thus improving the absorption capacity of the crop an important ways to control the problem.Watermelon is an important horticultural crop,widely cultivated all over the world.For proper plant growth,fruit yield and quality,potassium demand is required in large amount.Grafting improves resistance to low nutrients supply and is an important feature of melons horticultural crops.In this study,the experimental materials were consisting of two cultivars of watermelon K-efficient genotype ?Yong Shi‘,and K-inefficient genotype ?Zao Jia 8424‘;and two levels of K normal potassium?6 m M,contrast?and low potassium?0.01 m M,stress?were used.The purpose of our experiments was to study the feedback regulation mechanism of scion on rootstock during potassium uptake in grafted watermelon,response to low potassium micro RNA and long distance transportation of micro RNA.Potassium efficient absorption gene HAK5 under low potassium stress genes expressed in watermelon root system significantly increased the amount,thus verify its function.The main research results are as follows:1.Under different potassium levels scion influenced the root growth and physiology of rootstock.The results showed that: based on the concentration of potassium,scion influenced root growth rootstock of?potassium absorption capacity,and endogenous levels of ABA and IAA.We found that there are feedback regulation mechanism from scion to rootstock that affects potassium uptake in grafted watermelon.K-efficient genotype ?Yong Shi‘ as a scion can promote root growth of K-inefficient genotype ?Zao Jia 8424',potassium absorption ability,endogenous hormone levels of ABA and IAA.On the contrary,K-inefficient genotype ‘Zao Jia 8424' as a scion can reduce root growth of K-efficient genotype ‘Yong Shi',potassium absorption ability?endogenous hormone levels of ABA and IAA.This feedback mechanism was more obvious under low potassium stress conditions.2.Long distance movement of mi RNA in response to low potassium was analyzed by using RNA-Seq in response to low potassium.The results showed that: that K-efficient genotype ‘Yong Shi' leaf in response to low potassium mi RNA: mi R395 a,mi R395 b,mi R156a;root in response to low potassium mi RNA: mi R396 b,and novel₂4.K-inefficient genotype ‘Zao Jia 8424' leaf in response to low potassium mi RNA: mi R172 f,mi R172 a,mi R172 d,mi R395 a,mi R395 b,and mi R162;Root in response to low potassium mi RNA: mi R156 a,mi R167 c,mi R167 d,mi R396 b,mi R167 a,mi R395 b,mi R395 a,and mi R319 c.The differences of mi RNA are likely to be important mi RNAs watermelon in response to low potassium.Under low potassium stress more mi RNA regulation of plant growth and development proved that compared with K-efficient genotype ?Yong Shi‘,K-inefficient genotype ?Zao Jia 8424‘ is more sensitive to the low potassium stress environment.In response to K-efficient genotype ?Yong Shi‘ and K-inefficient genotype ?Zao Jia 8424‘ of low potassium mi RNA genes and their target genes expression quantity is found that mi RNA156 a and mi RNA395 b may be long distance transportation of mi RNA that scion on rootstock potassium uptake in grafted watermelon.3.Cloning and functional verification of HAK5 an important Watermelon potassium absorption gene.The results showed that: our study was successful to clone potassium absorption important genes of K-efficient genotype ?Yong Shi‘ in the genome HAK5?Cla012760?,and into T-DNA insertion mutants in Arabidopsis thaliana Salk₁30604,through transgenic Arabidopsis restored the mutant phenotype and potassium content in Arabidopsis thaliana plants,proved Cla012760 watermelon potassium absorption important genes.The experimental results show that the above: there is the phenomenon of feedback by scion on rootstock potassium uptake in grafted watermelon.K-efficient genotype ?Yong Shi‘ as scion promotes root morphology and physiological parameters of watermelon.On the contrary,K-inefficient genotype ?Zao Jia 8424‘ as scion on root morphology and physiological parameters of watermelon grafting has inhibitory effect.This phenomenon is more obvious under low potassium stress.There are mi RNA make a difference: mi R156 a,mi R162,mi R167 a,mi R167 c,mi R167 d,mi R172 a,mi R172 d,mi R172 f,mi R319 c,mi R395 a,mi R395 b,mi R396 b,novel₂4 when Watermelon after exposure to the low potassium stress.Thus these mi RNA may participate in the regulation of watermelon in response to low potassium.From the perspectives of shoot-root in response to low potassium mi RNA genes,mi RNA156 a and mi RNA395 b may be long distance transportation of mi RNA that scion on rootstock potassium uptake in grafted watermelon.Watermelon after potassium absorption important genes HAK5?Cla012760?expressed in root system significantly increased the potassium absorption under Low potassium stress,and genetically modified experiments verified the function,thus it is an important gene for potassium absorption of watermelon.