Study On The Regulation Of Plant Organs By GhSAP

Organ size is an important component of crop yield,and also a general problem in developmental biology.Plants regulate organ size by combine their own genetic mechanism to integrate internal growth signals with external environmental conditions to jointly regulate organ size.Study of organ size has always been a hot topic in the study of plant developmental biology.Plant organs,such as leaves,flowers and fruits,exhibit great changes in final size,which may reflect their gradual adaptation to the environment during evolution.The growth and development of plant organs include two consecutive stages:cell proliferation in the early stage and cell expansion in the later stage.Although some genes have been reported to be involved in the regulation of plant organ size,these genes are mainly concentrated in model plants including Arabidopsis and Oryza sativa.The regulation and molecular mechanism of plant size in non-model remain to be further studied.In our previous study,a gene(GhSAP)regulated seed size of Gossypium hirsutum was obtained by mapping cloning.Its homologous genes have been reported to be involved in the regulation of plant organ size in Arabidopsis,Cucumis sativus,capsella-rubella and other species,indicating the conservation of this gene.However,SAP showed complexity and diversity among species,and even among varieties.Therefore,it will be worthy to study on SAP by kinds of species.On the basis of the above background,this study intends to study the effect of GhSAP on plant organ size by using transgenic Arabidopsis thaliana,transgenic Brassica napus,and transgenic Oryza sativa as research materials,and combining with bioinformatics and molecular biology methods.The main findings are as follows:1.GhSAP target gene was cloned using genomicDNA of Gossypium hirsutum variety Yumian 1.The total length of the gene was 3406 bp.The CDS of GhSAP was cloned from the cDNA of Yumian 1.The total length of its CDS was 1362 bp,and the length of GhSAP protein is 453 aa.2.SAP homologous protein sequences from 53 species were obtained by Blast with a reference by GhSAP.These species are mainly dicotyledons,and are widely distributed in the family Cruciferae,Caragana,Rosaceae,Solanaceae,Leguminosae.Further analysis showed that the appearance of SAP originated before the emergence of flowering plants.3.The overexpression vector P_35S:GhSAP was constructed and was transformed into wild-type Arabidopsis thaliana and Brassica napus variety Westar.Four positive transformants of Arabidopsis were successfully obtained.Compared to wild-type,the leaves size increased in transgenic Arabidopsis plants,the whole leaves are hemispherical that could hardly be flattened.The length of hypocotyl and petiole,as well as the size of flower organ size,are also significantly increased.The silique of transgenic plants getting wider but shorter than the wild-type.4.Three positive transgenic Brassica napus plants were successfully obtained.Compared with the control,the leaves of transgenic plants didn't show significantly change in size,but the edge of leaves are getting mellower.In the later stages the plant height and the knot spacing are significantly increased,but the diameter of stem and the size of mature leaves are significantly decreased.In addition,the size of petals is larger and the siliques are wider and longer in transgenic plants than the control.5.The overexpression vector P_ubiquitin:GhSAP was constructed and was transformed into the Oryza sativa variety.Six positive transgenic plants were obtained,but they didn't show significantly different pheoptype than the control.Additionaly,the thousand grains weight of parts of transgenic plants is getting lower than the control.In the present study,we indicated that GhSAP could increase organ size in dicotyledons including Aradopsis thaliana and Brssica napus,but it didn't increase the organ size of monocotyledons such as Oryza sativa.This study lays a foundation for the subsequent study of the molecular mechanism of GhSAP on the regulation of plant organ size,and also provides genetic resources for high-yield breeding,which is helpful to the study of improving crop yield,which has far-reaching practical significance.