Transcriptome Analysis Of Tomato Tolerance To Low Phosphorus Stress

Phosphorus is an essential nutrient element for growth and development in plants.Although phosphorus is abundant in the Earth’s crust,it is usually in a form that cannot be absorbed by plants,greatly limiting the efficiency of phosphorus uptake by crops.People use chemical fertilizers to alleviate the phenomenon of insufficient phosphorus in the soil,but the excessive use of phosphorus fertilizers will cause environmental problems such as soil compaction and eutrophication of water.Phosphate rock is a non-renewable resource that is about to be depleted.Therefore,it is imperative to explore the molecular mechanism of lowphosphorus tolerance of crops and cultivate high-phosphorus varieties.As an important economic crop and model crop,tomato is of great significance to study the molecular mechanism of plant response to low phosphorus stress.We treated cultivated tomato（M82）and wild tomato（LA1589）with Low Phosphorus Hoagland Nutrient Solution,observed their phenotypes and measured their physiological and biochemical indicators.At the same time,through transcriptome sequencing of the shoot and root tips of M82 and LA1589 treated with low phosphorus,the differential genes significantly induced by low phosphorus stress were mined,and gene editing technology was used to create related gene mutant materials.The molecular mechanism of tomato tolerance to low phosphorus stress was preliminarily discussed.The specific results are as follows:（1）Low phosphorus inhibits tomato growth and promotes the accumulation of anthocyanins and reactive oxygen species.After 14 days of low phosphorus treatment,the growth of LA1589 was found to be better than that of M82,and the phosphorus absorption efficiency of LA1589 was stronger.Low phosphorus treatment enhanced the activities of SOD,CAT and POD in M82,and promoted the accumulation of anthocyanins,which indicated that LA1589 may have a certain ability to tolerate low phosphorus stress.（2）Low phosphorus promotes organic acid secretion and enhances phosphatase activity.Under low phosphorus stress,the root of LA1589 had a strong ability to secrete organic acids,and the activity of phosphatase was also significantly enhanced,which indicated that LA1589 might induction and secretion of phosphatases and organic acids to mobilize Pi from organic matter to adapt phosphorus starvation.（3）Low phosphorus induces expression of tomato phosphorus transporter genes.The expression levels of phosphorus-related genes in shoot and roots of the two materials were detected by q RT-PCR,and it was found that after low phosphorus treatment,most phosphorus uptake transporter genes,phosphorus starvation response genes,acid phosphatase genes The expression level was higher in LA1589 roots,which indicated that LA1589 had higher phosphorus absorption efficiency possibly due to the high expression of phosphorus transporter genes and acid phosphatase genes in roots.（4）By analyzing the transcriptome data of shoot and root tips after low phosphorus treatment of M82 and LA1589,we found that after low phosphorus treatment,1446 genes that were specifically induced in roots by M82 but not in LA1589,and 803 genes that were specifically induced in LA1589 but not in M82.There were 1334 genes that were specifically induced in M82 but not in LA1589 in shoot,and 1406 genes that were specifically induced in LA1589 but not in M82.Through cluster analysis of these differentially expressed genes,it was found that LA1589-specific expression genes were enriched in transmembrane transport,organic acid metabolism,phosphorus metabolism,chloroplast biosynthesis,shoot phylogeny and other pathways;M82-specific expression genes were enriched in osmotic stress,oxidative stress,DNA repair,flavonoid biosynthesis and other pathways.These results indicate that the response of tomato to low phosphorus stress is a very complex process.（5）Transcriptome analysis found that there were more differentially expressed genes encoding transcription factors after low phosphorus treatment.There are 494 in M82（136 in root,358 in leaf）,623 in LA1589（214 in root,409 in leaf）,of which MYB-related,b HLH,ERF,WRKY transcription factor families account for Most of them,this indicates that transcription factors may play an important role in the process of tomato response to low phosphorus stress.（6）Low phosphorus affects the expression level of nitrate transporter,and we also found the enrichment of the nitrogen transport genes in the GO analysis.To further explore the role of nitrogen in the response to low phosphorus stress,we constructed gene editing（CRISPR/Cas9）vectors for four nitrogen transporter genes,using Agrobacterium tumefaciens Tomato genetic transformation by transformation method.Currently,four genome editing（CRISPR/Cas9）vectors have obtained T0 generation plants.This study analyzed the differences in low phosphorus stress tolerance between cultivated tomato M82 and wild tomato LA1589,and provided a theoretical basis for further exploring the molecular mechanism of tomato low phosphorus stress tolerance.