Effects Of Silent PhPDS Gene On Growth And Development Of Petunia Hybrida

Carotenoid is a type of pigments which is widely found in nature and can be found much more in leaves,flowers,fruits and root of plants,which make the plant have both ornamental value and economic value.Carotenoid plays an important role in human and animal nutrition and health.High quality breeding of the horticultural crops in the future will base on the study of synthesis and regulation of carotenoid.Changing the content of carotenoid can cause the change of flowers color and increase ornamental value as well.The phytoene dehydrogenase is the key rate limiting enzyme and plays a central role in the biosynthesis of carotenoids.The encoded protein of phytoene dehydrogenase is located on the chloroplast thylakoid,which connected with the thylakoid membrane.When the gene of encoding protein is silent,the chloroplast lose the protective effect of this enzyme,and it can lead to the degradation of chlorophyll,and appear the photobleaching phenomenon,which make the leaves and sepals be mottled,faded,yellowing even white.Therefore,PDS is often used as a Marker gene in plants study,but whether it is suitable for petunia growth and development research have not been reported;without intuitive changes after silencing PDS,whether it will affect the cells,chloroplast and other microscopic changes have not yet in-depth.In this study,we used the mature VIGS technique of our laboratory to explore the specific effect of PhPDS on growth and development of petunia by sliencing.The results are as follows:(1)The plant phenotype changed obvious by PhPDS silencing,the leaves and sepals lost green.With the plants continue to grow,the leaves would not return to green;the content of chlorophyll and carotenoid were reduced,Chla/b was greater than the control,and the mesophyll cells were blue under an optical microscope.There were red and white two color flowers on one plant,when the flowers were white while the leaves were green,when the leaves were white,and the flowers were red.In addition,the new leaves of the stems with white leaves would still change to white after in vitro culture,indicating that the effect of VIGS remain unchanged after in vitro.(2)The leaves of the plant after the silence of PhPDS were rugged,the size and the number of cells had changed at different developmental stages,and the thickness of leaf had increased.PhPDS affects the cell development of leaf.(3)After PhPDS silencing,it was found that the leaves were senescent a nd mildew acceleratly through the aging observation of multiple groups of leaves in vitro.(4)After the silence of PhPDS,the ultrastructural observation showed that the green part of the mottled leaves was the same as the control.The chloroplast number and the internal structure of the different stages were different,and the number of chloroplasts increased in the little leaves and young leaves,almost no starch granules existed.In mature leaves,the number of chloroplasts was significantly decreased,and also had no starch granules,and the chloroplast structure changed and the thylakoid was absent,and the granum decreased significantly and even lost.PhPDS affects the growth of petunias chloroplasts.(5)The contents of ion Cd,Co,Mo and Zn were significantly increased in the leaves,and Ca and Mg were decreased.Mo and Fe in the safflower with white leaves increased significantly,while Cd markedly decreased.Indicating that PhPDS in different tissues of petunia have the effect of resisting heavy metal hazards.