Functional Identification Of Trihelix Transcription Factor SlPTL In The Regulation Of Growth Development And Abiotic Stress In Tomato

Tomato is a widely cultivated worldwide economic crop,which occupies a pivotal position in the vegetable industry.It is also one of the important model crops for plant science research.It is of great theoretical and practical value to improve tomato or other new varieties of solanaceous plants by excavating the excellent stress-resistance genes of wild-type tomato resources and carrying out functional studies.Transcription factors play an important role in regulating the growth development and in response to stresses and many other aspects.However,functional studies of trihelix transcription factors in model crop tomato have rarely been reported.In this study,a trihelix transcription factor was cloned from wild-type tomato.Based on its homologous gene in Arabidopsis,it was named SlPTL.The silencing vector of this gene was constructed using RNAi technology,and the tomato genetic transformation was mediated by Agrobacterium tumefaciens?strain LBA4404?.The SlPTL silencing transgenic plants were finally successfully obtained,and their functions in tomato growth and abiotic stresses were preliminary identified and analyzed.The main results obtained in this study are as follows:?1?Phylogenetic tree analysis with Arabidopsis and rice showed that trihelix family genes were divided into five groups?GT-1,GT?,GT-2,SH4,and SIP1?,among these groups,SlPTL belongs to GT-2 subfamily.It is consistent with the multiple sequence alignment shown that SlPTL containeds conserved N-and C-terminal trihelix DNA-binding domains and an intervening central coiled-coil region.?2?The expression patterns of SlPTL were analyzed using qRT-PCR technique,GA₃,IAA,ABA,MeJA and ACC hormone treatments,and drought and salt stress treatments of wild-type tomato seedings can all induce SlPTL expression to different degrees,indicating that SlPTL may be involved in hormone response and abiotic stress response.The expression pattern of SlPTL in tomato tissues and organs was analyzed,the results showed that the expression level of SlPTL was the highest in roots,followed by stems.The expression levels of SlPTL were relatively low during the development of young leaves to senescent leaves and flowers to fruits,which showed a down trend.In addition,the expression level of SlPTL in four-whorl floral organs?sepals,petals,stamens and pistils?was further analyzed,indicating that it was expressed in floral organs,with the highest relative expression in stamens.These results suggest that SlPTL may play a role in the growth and stress response processes in tomato.?3?SlPTL silencing vector was constructed and the transgenic lines with high silencing efficiency were obtained by genetic transformation.Compared with wild-type plants,down-regulation of SlPTL conferred pleiotropic phenotypes,including dwarfism,shorter internodes,increased leaf number and decreased leaflets size,shorter petioles.Analysis of stem tissue sections revealed that the xylem cell layer of the SlPTL-silenced transgenic lines was thicker than wild type,and the pith cells were relatively shorter and tighter.?4?According to the dwarf phenotype of the SlPTL-silenced transgenic lines,we examined the expression levels of some genes related to gibberellin synthesis,metabolism and signal transduction.The results indicated that silencing of SlPTL affects the expression of these genes,resulting in gibberellin deficiency phenotype.The dwarf phenotype of SlPTL-silenced transgenic plants can be restored after spraying exogenous GA₃,indicating that the dwarf of transgenic plants is a type of GA₃-sensitive.?5?The length of the sepals of the transgenic plants was shorter than that of the wild-type tomato,and the average seed number of the fruits was reduced.For this reason,the expression level of SlPTL at different developmental stages of the flower was further analyzed.The results showed that with the development of flower buds,it showed a downward trend.Pollen germination experiments showed that the transgenic plants had lower pollen germination rates than wild-type plants,and the expression of pollen development-related genes was also suppressed.These results indicate that silencing of SlPTL interferes with pollen development in tomato and thus affect seed development in tomato.?6?Based on a large number expression of SlPTL in roots and the response pattern of stress,forty-day-old plants were subjected to stress tests.It was found that the drought-resistance and salt-tolerance of the silencing transgenic plants were significantly stronger than that of the control.SlPTL-silenced transgenic plants had better growth status,higher relative water content and lower leaf water loss rate,and most of the stress-related genes also showed up-regulation,these results also supported their stress resistance.In summary,this paper explored and studied the function and mechanism of tomato plant trihelix transcription factor SlPTL in regulating tomato plant growth and abiotic stress response,laying a certain theory for further expanding plant trihelix family function research,which provides genetic resources for the use of genetic engineering technology to improve crop agriculture traits.