Tomato SlMYBL Plays An Important Role In Fruit Quality And Drought Stress Responses

Drought ranks first among the natural disasters affecting plant growth and fruit development.According to statistics,the crop yield reduction caused by drought can reach more than 50%.Meanwhile,drought will also lead to the decline of fruit size and nutritional quality.Tomato is one of the important cash crops in China and have a large content of nutrients,including vitamins and phenolic compounds.It has important nutritional and economic value.At the same time,it is also an important model to study fruit development and nutritional quality.With the rapid development of molecular biology,using transgenic engineering technology to genetically modify tomato to improve plant drought resistance has become a research hotspot of molecular biology.In this study,the role of tomato MYBL gene in fruit quality and drought stress responses was studied by means of genetic engineering,genetics and molecular biology.Firstly,we analyzed the expression of Sl MYBL gene in different tissues of tomato plants by q PCR technology.The results showed that the gene was expressed in different tissues of tomato plants.To further analyze the biological function of Sl MYBL gene,we constructed the overexpression vector of Sl MYBL gene,and gave the Sl MYBL co-suppressed(Sl MYBL-cs)transgenic lines in Micro-Tom.Sl MYBL-cs transgenic lines displayed dwarf phenotypes.The fruit size and weight and lycopene in fruit of Sl MYBL-cs transgenic lines were all decreased compared to wild-type.These results showed that Sl MYBL gene may be involving in regulating fruit quality.Secondly,we found the expression level of Sl MYBL gene was significantly upregulated after PEG6000 treatment wild-type tomato plants.We speculated that slmybl gene may be involved in the response of plants to drought stress.Therefore,We constructed the CRISPR/Cas vector of Sl MYBL and gave Sl MYBL knockout transgenic tomato lines(slmybl-cr).It was found that slmybl-cr transgenic tomato plants also had dwarf phenotypes and showed a more sensitive phenotype than wild-type under drought stress.At the same time,the physiological indexes of wild-type and slmybl-cr transgenic tomato plants under drought stress were determined.The results showed that the relative water content,proline content and antioxidant enzyme activity of slmybl-cr transgenic tomato plants were lower than those of wild type.Meanwhile,the contents of reactive oxygen species and malondialdehyde of slmybl-cr transgenic lines were higher than those of wild type.These results displayed that Sl MYBL gene was involved in regulating drought stress responses,and confirmed that Sl MYBL knockout transgenic plants were more sensitive to drought stress.Stomatal regulation is one of the mechanisms for plants to defense response against drought stress and adapt to the environment.Plants can regulate leaf transpiration rate by controlling stomatal density and opening and closing the pores,and affect leaf water potential.When wild-type and slmybl-cr transgenic tomato lines was treated using PEG6000 or ABA,the stomatal density of slmybl-cr transgenic lines were significantly higher than wild-type.The stomatal closure of slmybl-cr transgenic lines were significantly smaller than wild-type.And the water loss of slmybl-cr transgenic lines was faster than wild-type.Previous studies have shown that ABA can affect drought stress responses of plants by regulating opening and closing the pores.So,we analyzed the ABA content and the expression level of ABA biosynthesis related genes in slmybl-cr transgenic lines.It was found that the ABA content and the expression level of ABA related genes(Sl NCED1 and Sl PYL4)in slmybl-cr transgenic tomato plants decreased significantly.In conclusion,MYB transcription factor Sl MYBL can affect tomato plant growth,development and fruit quality.Moreover,Sl MYBL gene can participate in the response to drought stress through ABA mediated stomatal movement.This study clarify the biological function of Sl MYBL gene,reveal the role of Sl MYBL gene in fruit quality and the molecular mechanism of Sl MYBL gene involving in drought stress responses,provide theoretical basis for genetic improvement of tomato varieties.