Analysis Of Floral Development Related LBD And COBL Gene Families In Jatropha Curcas

Jatropha curcas L.,a plant of the family Euphorbiaceae,is considered an excellent raw material for biodiesel production due to the high oil content in its seeds(40%)and no pollution after burning.However,the ratio of female to male in J.curcas is only 1:29-1:13,which directly leads to the low yield of J.curcas.It severely hinders development and utilization of J.curcas.The development of female flowers in J.curcas needd to undergo stamen abortion.Therefore,it is significant to reveal the mechanism of stamen development in J.curcas.In this study,1290 stamen-specific expression genes of J.curcas were screened,and then gene function analysis and conservative analysis were performed for these genes.Next,based on the analysis results and previous studies,we selected LBD and COBL gene families from the stamen specific expression genes that may be related to the male flower development of J.curcas for further analyses in Euphorbiaceae plants,including phylogeny analysis,evolutionary expansion analysis,preliminary function prediction and function verification.And these Euphorbiaceae plants include J.curcas,Hevea brasiliensis(rubber tree),Manihot esculenta Crantz(cassava)and Ricinus communis(castor).The main results of these analyses are listed as following:(1)The stamen-specific expressed genes in J.curcas mainly encode the enzymes.The KEGG enrichment results showed that these genes were mainly involved in carbohydrate metabolism.Compared to Arabidopsis thaliana,Amborella trichopoda,tomato and maize,there were fewer stamen-expressed gene orthogroups in J.curcas.And the stamen development genes of J.curcas were relatively similar to those of A.thaliana.(2)The phylogenetic analysis showed that both Euphorbiaceae LBD and COBL proteins tended to cluster together in the phylogenetic tree.The protein motifs of Euphorbiaceae LBD were slightly different from those of A.thaliana;whereas the protein motifs and gene structure of Euphorbiaceae COBL and A.thaliana COBL were conservative.And all four species of Euphorbiaceae had COBL genes regulated by miRNA156.In addition,LBD genes in the same subclass have similar expression profiles in J.curcas.The class Ⅰa and class Ⅰe genes were mainly expressed in male and female flowers.The tissue expression of different COBL genes varies greatly,JcCOBL2 and JcCOBL5 mainly expressed in male flowers.(3)The results of protein subcellular localization showed that the LBD proteins of J curcas were mainly localized in the nucleus.Overexpression of JcLBD1 or JcLBD11 in lbd10 in A.thaliana resulted in a higher rate of pollen abortion.And overexpression of JcLBD28 or JcLBD32 in lbd10 mutant decreased the rate of pollen abortion..Our results suggest that the LBD gene family may affect floral development in J.curcas.JcLBD1,JcLBD11,JcLBD28,and JcLBD32 are likely related to pollen development.COBL genes may regulate the development of pollen tubes in J.curcas,but it remains to be further verified.Our study provides a new theoretical basis for the study of the floral development mechanism of J.curcas.And it provides a new idea for the study of the mechanism of sexual differentiation.