The Regulation Of Tomato Root Development

Tomato is one of the most cultivated vegetables in the world with high nutritional value.Tomato cultivation in China is extremely extensive,and China is the largest production of tomatoes country.Tomato and tomato products have unique flavor,and they are very important for health.Recent economic development in China greatly improved tomato demand.Thus it's very important to improve the quality and production of tomato.Root is one of the most important organs in plant,and it can directly affect the growth and development of aerial parts.Currently the research on tomato mainly focus on the fruit.In order to study how the root affects the growth and development of tomato we use both genetic and molecular techniques to study the tomato root development,including root patterning and root hair development.This research is of great significance to improving the production and quality of tomato.The main results of this study are as follows:First,utilizing histological methods and microscopy techniques,we found that the radial patterning of the tomato root was similar to that of the model plant Arabidopsis.However,Arabidopsis roots have only one simple layer of cortical cells,while tomato roots have multiple layers of cortical cells.Interestingly,different ecotypes of tomato had different number of cortical cells,ranging from 2-5 layers.Furthermore,we found that the layer of cells neighboring the vascular bundle had the Casparian strip that is unique to the endodermis,which was consistent with Arabidopsis thaliana.Second,we made a number of vectors including pSHRLIKE::GFP-GUS,p35S::SHR::GFP and inducible expression vector,pG1090-XVE::SHR.And we successfully transformed those genes into Arabidopsis thaliana and Tomato hairy roots.Thirdly,the expression of pSHRLIKE::GUS-GFP by GUS staining was observed by a compound microscope.We found that the expression pattern of SHRLIKE in tomato root system was obvious in the root vascular tissue,which is consistent with that in the root of Arabidopsis thaliana,indicating that the promoter activation is conserved among species.Fourth,overexpression of Arabidopsis SHR showed that it can induce enormous periclinal cell division.By induction of SHR expression,we found that cortical cells were the most sensitive cell layer to SHR,with the first visible periclinal division during the induction.Fifth,through the exogenous application of gibberellin,gibberellin synthesis inhibitor paclobutrazol(PAC)and ABA,we found that different hormones can affect SHR-mediated periclinal cell division.Compared with the control,gibberellin inhibited SHR-promoted periclinal cell divisin,while inhibition of gibberellin synthesis by PAC increased periclinal cell division,indicating that gibberellin signaling is likely involved in the periclinal cell division mediated by SHR.Six,we found that the application of either PAC or ABA can significantly promote the initiation of tomato root hair.In contrast,the application of gibberellin can reduce the number of root hair,indicating that the root hair production in tomato is regulated by GA and ABA signaling.In summary,we examined the regulation of root radial patterning in tomato and Arabidopsis thaliana.Our results suggested the existence of an evolutionarily conserved regulation mediated by SHR in root radial patterning in tomato and Arabidopsis.Our work laid the foundation for future optimization of root structure to improve the production and quality in horticulture species like tomato.