Role Of SlSWEET12c And SlSWEET14 In Sugar Transport And Accumulation Of Tomato Fruits During Maturation

SWEETs(Sugars Will Eventually Be Exported Transporters)is a kind of sugar transporters which are involved in plant biological processes and plays key roles in plant growth and development in response to various stresses and host-pathogen interaction.Both SlSWEET12 c and SlSWEET14 belong to the CladeIII of the SWEETs family and mainly transport sucrose.In order to better understand the function of SlSWEET12 c and SlSWEET14 genes,the full-length coding sequences of SlSWEET12 c and SlSWEET14 genes were cloned in fruits from Micro-Tom(Solanum lycopersicum)tomato by using RT-PCR.Real-time quantitative PCR is used to identify the spatio-temporal expression characteristics in the fruit during fruit mature stage,and the silencing vector and overexpression vector are constructed and transformed into tomato by Agrobacterium-mediated genetic transformation after the efficiency of two vectors is examined by the transient expression of Agrobacterium tumefaciens injection method;so that obtaining transgenic plants of SlSWEET12 c and SlSWEET14.The expressions of SlSWEET12 c and SlSWEET14 in transgenic fruits are studied by quantitative PCR.The changes of sugar composition and content in transgenic leaves and fruits are detected by high performance liquid chromatography.The main findings are as follows:1)Analysis of spatio-temporal expression characteristics shows that the SlSWEET12 c gene is prominently up-regulation at the red riping stage during tomato fruits development,and the highest expression level of SlSWEET12 c is in sarcocarp,and secondly expresses in ventricular dissepiment,revealing that SlSWEET12 c may regulate the loading of sugar into the phloem tissue of the tissue and the transportation and unloading of parenchyma.Through tomato genetic transformation and positive PCR detection to obtain tomato transgenic materials of overexpression and silencing vectors of Sl SWEET12 c and SlSWEET14.Eight overexpression lines and eighteen silencing lines of SlSWEET12 c were obtained by PCR.SlSWEET14 transgenic lines identified that overexpression lines are fifteen and silencing lines are twenty.The real-time quantitative analysis of Sl SWEET12 c silencing transgenic red riping fruits shows that the expression level of transgenic lines are 1.3~3.8 times lower than control,Analysis of the sugar content of leaves and fruits at the red riping stage of SlSWEET12 c silencing plants showed that the content of fructose in mature leaves of SlSWEET12 c silencing strain showed an upward trend,but content of glucose and sucrose are decreased.The content of glucose and sucrose and the fructose and glucose in red riping fruits is increased,but sucrose content are decreased.The results indicates that SlSWEET12 c can transport sucrose.2)The maxium expression level of SlSWEET14 is found by qRT-PCR at the mature green stage of fruit,among which the highest level of expression is in the colloidal placenta of the fruit,followes by the fruit stem.This indicates that SlSWEET14 may play an important regulatory role in the loading of sucrose into the phloem of the source tissue and the transport and unloading of the colloidal placenta and fruit pedicel.Through tomato genetic transformation and positive PCR detection to obtain tomato transgenic materials of overexpression and silencing vectors of SlSWEET14.SlSWEET14 transgenic lines identified that overexpression lines are fifteen and silencing lines are twenty.while the expression levels of mature green fruit are significantly reduced in silencing transgenic tomato SlSWEET14 that is 2.3 to 12.5 times as low as control.The result was used to further verify that the target gene was integrated into the tomato genome.The sugar content in leaves and mature green of S1SWEET14 silencing plants showed that the contents of fructose,glucose and sucrose in leaves of SlSWEET14 are lower than those in wild type,while the fructose and glucose contents are increased significantly in mature green fruits.The results reveals that SlSWEET14 may transport sucrose.The contents of sucrose in the fruits of SlSWEET12 c and SlSWEET14 were reduced,indicating that the inhibition of the expression of SlSWEET12 c and SlSWEET14 can result in a decrease in the transport of sucrose from leaves to fruits,which could regulate the transport of sugar from source to sink.