Functional Analysis Of Transcription Factor CsMYB44 For Regulating Wax Biosynthesis In Horticultural Plants

As the first barrier contacting with the outside world,plant epidermal wax plays an important role in the resistance to biotic and abiotic stresses,plant growth and development.We have previously found a transcription factor Cs MYB44 by trancriptomic and metabolomic analysis on a citrus glossy mutant,which was significantly down regulated in the mutant,and could regulate the wax biosynthesis.We further used horticultural plants tomato and citrus as well as model plant Arabidopsis to dissect the function of Cs MYB44 and explored its regulatory mechanism in wax biosynthesis.The results are as follows:(1)Phylogenetic analysis and subcellular localization of Cs MYB44:It is found that Cs MYB44 belongs to subfamily 22 of R2R3-MYB family,which is related to plant response to stress;protein of Cs MYB44 is mainly located in the nucleus.(2)Phenotypic analysis of Cs MYB44 overexpression line of citrus callus:The transgenic Citrus Calli with overexpressed Cs MYB44 was obtained.Potential target genes Cs PLC4 and Cs KCS1 regulated by Cs MYB44 were predicted by gene expression analysis.It was verified that Cs MYB44 did not interact with candidate genes by dual-luciferase assay.(3)Phenotypic analysis of Arabidopsis Cs MYB44 overexpression line:It was found that the penetration rate of Cs MYB44 overexpression line was lower than that of wild type,suggesting the change of cuticle;according to the observation of Transmission electron microscope(TEM),the wax crystal on the leaf surface of overexpressed strain was less than that of wild type,which suggested that Cs MYB44 acted on the wax pathway.(4)Phenotypic analysis of tomato Cs MYB44 overexpression line:The transgenic tomato plants with overexpressed Cs MYB44 were obtained.It was confirmed by TEM that the accumulation of wax crystals on the leaf surface of Cs MYB44 overexpression line was more than that of wild type,which indicated that Cs MYB44 may play a positive role in the regulation of wax biosynthesis.(5)Yeast two hybrid assay to explore genes interacted with Cs MYB44:Cs ERF3,a transcription factor interacting with Cs MYB44,was identfied by yeast two hybrid screening system,which provided a new research direction for wax transcription regulation.