Comparision Of The Effects Of Several Volatile Materials On Sprouting Inhibition Of Potato Tubers And Research On The Acting Mechanism

Potato(Solanum tuberosum L.)is the fourth most important food crop in the world due to its high yield,extensive adaptability,starch content.Fresh or industrial processing of tubers results in a reduction or loss of their commercial value due to sprouting.Therefore,the regulation to tuber dormancy and sprouting is critical for potato industry development.Dormancy and sprouting comprise a complex set of physiological processes that are regulated by endogenous hormones,but the understanding to this stat transition is still unclear.To investigate the mechanisms underlying the effects of the novel sprout inhibitors and search for the important metabolism process and genes regulating the physiological stats transition,RNA-seq(Illumina Solexa)were used to study different expression genes and analysis expression pattern changes in different varieties.The mainly results as follows:(1)The sprout inhibition potencies were as follows:menthol(MEN)>camphor(CAM)>naphthalene.Bud growth was not detected in response to menthol treatment,but 1-2-mm shoots with no formation of the apical meristem region were observed following treatment with camphor,then the top of bud could not grow and started to become necrotic with vacuolization of the internal cells and all of the buds were dead after 80 d.when removed CAM and NAP treatment,germination would be recoverable.Vessels in the tuber,especially parts connecting the bud and tuber flesh,appeared to be damaged.This phenomenon may hinder access to the nutrient supply,further reducing the resistance of the bud to external stress.In addition,the number of starch grains in aging tuber parenchymal cells decreased with the nutrient consumption for bud growth,whereas no obvious change was detected in response to camphor treatment.This phenomenon may have been caused by the sprout inhibition,which reduced the nutritional consumption and prevented starch degradation via feedback inhibition.CAM,been able to sprout inhibition,but not reverse downward trend of abscisic acid(ABA)content with dormancy release,but can reduce the magnitude of the increase GAs.(2)Differential gene expression analysis was performed on dormant(D),sprouting(S)and CAM treatment(T)stats.There were total 3705 up-regulated genes,222 down-regulated genes in S and D comparison(D-VS-S),208 up-regulated genes,5422 down-regulated genes in T and S comparison(S-VS-T)and 3151 up-regulated genes,883 down-regulated genes in T and D comparison D-VS-T.Comparing differences in gene number and the proportion of down or up-regulated genes derived that T and S expression profiles was closer,indicated that although CAM treatment can inhibit bud but could not reversed dormancy release.Plant hormone signal transduction was the most significantly enriched pathway of up-regulated differential expression genes for tuber transition from dormancy to germination,indicted that several categories of hormones were involved in tuber physiological state transition.Camphor treatment inhibited those genes expression,but most of genes still higher than dormant tubers.In addition,Phenylpropanoid biosynthesis,Phenylalanine metabolism,Starch and sucrose metabolism,Fatty acid elongation,Steroid biosynthesis pathways also involved in dormancy release and sprouting.Significant inhibition of Cutin,suberine and wax biosynthesis in camphor treatment indicated that cuticle formation,as one of skin protection organizations,was blocked,which was the reason of shoot apical necrosis in the molecular level.(3)Study on 29 gene variation patterns with the storage time in different varieties and sprout-inhibitor treatments using qRT-PCR were completed.Expression patterns of SMO1,STE1,DWF1,85A1/2 genes involved in brassinosteroid(BR)synthetic indicated BR is closely related with the tubers dormant release,and the BR synthesis time of long dormant varieties was late 28d-42d than that of short dormancy varieties.These five genes BRI1,BSK1,BZR1/2,TCH4 and CYCD3,participation BR signal transduction,only BRI1,CYCD3 expression patterns were consistent with the synthetic gene in the three varieties.The expression of other genes was different from the synthetic gene and had strain-specific characteristics.The expression of BSK1 in FR was elevated,but no significant changes in ML and BS,remaining at moderate levels of expression in the entire storage period.Sprout-inhibitor treatment could promote these gene expression at different levels in early storage(7-21d)and the promoting effect of CAM treatment was greater than that of MEN treatment(and contrast with sprout-inhibiting ability),but after all rapid decline and remain at low level.4? treatment also suppressed the expression of these genes and maintained at low level.24-eBL(24-epibrassinolide)treatment could release tuber bud dormancy,but do not promote shoot elongation growth.Expression pattern of genes PME,PG,PEL participation pectin degradation was similar to BR synthetic gene,but can be achieved a high value before germination.Such as PME,PG in BS was 382.63 and 712.40 folds at 63 d comparing to dormancy potato.The cell wall softening of the storage cells was earlier than bud germination,suggesting that this may be more conducive to mass transport.Changing patterns of CYP77A6,HPTF and WES genes involved in the formation of cuticle formation in different varieties was similar to the trend of above genes,increasing with storage,but some fluctuations in the middle of storage.CAM,MEN and refrigerated treatment inhibited expression of these genes mainly in the medium or late terms,inhibiting ability was directly proportional to the capacity to sprout inhibition.(4)Transcripts of the ACC(aminocyclopropane carboxylate)oxidase gene ACO,which is related to the synthesis of ethylene;transcription factor AGBP3 and the polyphenol oxidase gene PPO were found to increase with dormancy release.The expression of these genes was significantly inhibited in response to the camphor and menthol treatments compared to the control in the same period.AGBP3 fold of the long-dormant varieties ML and the BS rises much higher than short-dormant varieties FR(FR 174.09,ML 1121.93,BS 2683),speculated that the transcription factors are closely related with bud germination.Transcription factor WRKY75,pathogenesis-related proteins gene STH-2 and unknown-function gene BUK are induced by CAM and had reached the highest value at the date of tuber sprouting,this result indicated that these genes may cause resistance against CAM by newborn shoots.MEN treatment will not sprouting,but BUK was induced to expression in the period of dormancy and germination.The expression of the cell cycle inhibitor KRP4(Kip-related protein 4)decreased in both the CK and camphor treatment group during storage but significantly increased in response to menthol treatment,by approximately 1.6-15.9-fold,SN2 was regularly dropped significantly from dormant to sprout and the expression of three varieties at sprouting date only accounted for 3.61%,1.00%,1.63%of dormancy,respectively.The expression of this gene also decreased during storage in CAM and MEN treatments,but the speed slows and higher than that in CK after 35 d.4? treatment made KRP4,SN2 maintained at a high level,20.5 folds and 17.17 folds comparing to CK at the same period respectively.