Identification And Gene Function Analysis Of Arabidopsis Db5 Mutant

Carotenoid as an important natural pigment,can found in all photosynthetic tissues.It is involved in a wide range of physiological processes,including light absorption,transmission,photoprotection,coloring animal.In addition,carotenoid also act as strigolactones(SLs)and abscisic acid(ABA)precursors involved in plant growth regulation and interaction of plant with their environment.Although early biochemical studies let us have a full understanding of the carotenoids,but we know very little about the genetic basis of Arabidopsis carotenoid biosynthesis pathway.In this study,we get Arabidopsis db5 mutant gene AtZISO and found the mutated base(G to A)in fourth exon region by map-based cloning,which give rise to a amino acid changes(G to E),a extreme conservative amino acid in a variety of species.Subsequently,we construction of AtZISO overexpression vector,and then get transgenic plant of Col or db5 mutant background by GV3101 Agrobacterium-mediated transformation.Overexpression AtZISO can restore db5 mutant defective phenotype,this result further confirm db5 mutant defective phenotype is caused by AtZISO mutation.In addition,we also constructed overexpression vectors of carotenoids biosynthesis pathway genes PSY and CRTISO for in-depth study of AtZISO function,are defined desaturase and isomerase respectively.AtZISO as a carotenoid biosynthetic pathway isomerase involved in 9,15,9 '-tri-cis-?-carotene transform to 9,9'-two-cis-?-Carrots isomerization prime.Some studies indicate that this isomerization can be carried by light,but enzymatic isomerization is indispensable in other non-photosynthetic apparatus of plastids,.Previous study showed that AtZISO mutant zicl-1 appeared cotyledon bleaching and delayed ture leaf greening when grown in dark and light respectively.However,we unknown whether the AtZISO have other function.In this paper,we also found AtZISO caused a series of loss-of function phenotype under normal growth conditions?Such as db5 have normal cotyledons,yellow true leaf;in addition,db5 inflorescence stems and pods phenomenon also appears yellow;compared with Col,db5 individual short,many branches of whole seedling showing yellowish phenomenon;db5 appeared aging phenotypes.NADPH is produced by photosynthesis in plants,and O2 is catalytic for NADPH oxidase to produce H2O2.In 20?mol·m-2·s-1 light would lead to db5 mutant etiolation leaves and aboveground part of the seedlings appeared H2O2 content reduce phenomenon,but the green fully expanded rosette leaves have no obvious change in H2O2 content.Fv/Fm detected show the db5 mutant and wild type Col photosynthesis is not different in green fully expanded rosette leaves,these reslults indicated that AtZISO genes affected on synthesis of carotenoid and finally influenced the photosynthesis of plants.In this paper,our results showed that the Arabidopsis AtZISO isomerase on plant photosynthetic organ under the light isomerization of carotenoids are essential,which is consistent with the result of some previous studies.In addition,we found that the db5 mutant anti-aging phenotype,this result suggested that AtZISO mutation are likely to affect some of the plant hormone synthesis in carotenoids as precursors.