Preliminary Study On SlMYB64 Involved In Plant Grouth And Pollen Germination In Tomato

Tomato(Solanum lycopersicum)is one of the most widely cultivated vegetables in the world.It is very popular due to its rich nutrient and good flavor.Pollen development is crucial for sexual reproduction of flowering plants.Pollen germination and pollen tube growth are the precondition to complete the double fertilization.MYB transcription factor family is one of the largest families in plants,widely involved in plant growth and development,abiotic stress responses,hormone regulation and secondary metabolite biosynthesis.But it is not clear whether tomato MYB transcription factors regulate pollen development.Previous study reported that SlMYB64,a tomato R2R3-MYB transcription factor,responsed to low temperature and salt stress.In order to further study its function,Sl MYB64 was overexpressed in Micro-Tom(a miniature dwarf tomato)and gained 7 T1 transgenic lines,but the fruits had no fertile seeds.Then it was found that pollen vitality and germination rate were significantly reduced and pollen apertures were abnormal in Sl MYB64 transgenic lines.In order to gain transgenic seeds,Sl MYB64 was transferred into another tomato inbred line with bigger yellow fruits and 17 T1 transgenic lines were obtained.Three T2 transgenic lines with different expression levels of Sl MYB64 were selected to conduct correlation experiments.Data showed that pollen viability of T2 transgenic plants was decreased significantly compared with wild type by Alexander staining;And pollen germination rate of T2 transgenic plants was significantly reduced: the pollen germination rate of wild-type was about 90% by pollen in vitro assay,while the rates of the three T2 transgenic lines were 80%,63% and 20% respectively.Scanning electron micrographs displayed that Sl MYB64 affected the development of pollen aperture,86% of pollens from wild type had normal germination apertures,while only 36% of pollen from OE-3,the transgenic line with high espression level of Sl MYB64 amomg the three.Paraffin section showed that anther structure was no obvious change at stage 16,18,19 and 20 in transgenic lines.In addition to the defect of pollen grains,SlMYB64 T2 overexpression lines also appeared dwarf phenotype.Tissue specific expression analysis showed that Sl MYB64 was high expressed in hypocotyl,leaf and carpel by real-time fluorescent quantitative PCR,indicating that it might participate in leaf and flower development.Overall,this study revealed that SlMYB64,a R2R3-MYB transcription factor,affected pollen development in tomato,which laid a foundation for further studying its function in pollen development in tomato.