The AGL6-like gene OsMADS6 regulates floral organ and meristem identities in rice

Although AGAMOUS-LIKE6 (AGL6) MADS-box genes are ancient with wide distributions in gymnosperms and angiosperms, their functions remain poorly understood. Here, we show the biological role of the AGL6-1ike gene, OsMADS6, in specifying floral organ and meristem identities in rice (Oryza sativa L.). OsMADS6 was strongly ex- pressed in the floral meristem at early stages. Subsequently, OsMADS6 transcripts were mainly detectable in paleas, lodicules, carpels and the integument of ovule, as well as in the receptacle. Compared to wild type plants, osmads6 mutants displayed altered palea identity, extra glume-like or mosaic organs, abnormal carpel development and loss of floral meristem determinacy. Strikingly, mutation of a SEPALLATA (SEP)-like gene, OsMADS1 (LHS1), enhanced the defect of osmads6 flowers, and no inner floral organs or glume-like structures were observed in whorls 2 and 3 of osmadsl-z osmads6-1 flowers. Furthermore, the osmadsl-z osmads6-1 double mutants developed severely indetermi- nate floral meristems. Our finding, therefore, suggests that the ancient OsMADS6 gene is able to specify "floral state" by determining floral organ and meristem identities in monocot crop rice together with OsMADS1.

Expression and Interaction Analysis of FAZ1 Protein in Brassica oleracea

To identify and characterize genes involved in reproductive tissue abscission in Brassica oleracea,the transcript data of pollinated pistil was analyzed.A differentially expressed gene,named BoFAZ1(FLOWER ABSCISSION ZONE1)was identified,which contains one exon and encompass a 139aa.Furthermore,a T-DNA insertion mutant(SALK_302_G01)(faz1 mutant)was obtained from Arabidopsis thaliana mutant library.Floral organ shedding from mutants was delayed and a V-shaped structure in the boundary region between the stalk and torus of the sepal abscission zone was obtained in faz1 mutant.The cell density of this structure was lower than that of the corresponding region in the wild-type control.In the transgenic plants,the normal development of the stalk zone of faz1 was recovered completely by transforming a 1919-bp DNA fragment of BoFAZ1 into the faz1 mutant.In Addition,our data showed that BoFAZ1 was expressed in mature pollen grains,but not in the bracts,roots,stems,leaves,and sepals.Its expression in the filaments,stigma,and pistil exfoliation layer gradually increased after pollination.Subcellular localization experiments showed that BoFAZ1 was located in the cell membrane.A myristoylation site was found at the N-terminus of BoFAZ1.Removal of this site resulted in protein dislocation in the cytoplasm,cell membrane and nucleus.Finally,a yeast two-hybrid test indicated that BoH3.2(histone H3.2),a protein involved in abscission zone development,interacted with BoFAZ1.This interaction was verified by a GST pull-down assay.In summary,our data indicated that BoFAZ1 was involved in the formation of the pistil abscission zone in B.oleracea.

Cloning and Functional Analysis of the MADS-box CiMADS9 Gene from Carya illinoinensis

A MADS-box gene,CiMADS9,was cloned from the male flowers of Carya illinoinensis by rapid amplification of cDNA ends. The gene was 1 077 bp with a 768 bp open reading frame encoding 255 amino acids. Multiple sequence comparisons revealed that Ci MADS9 is a typical MIKC-type MADS-box gene with a MADS-box domain and a K semi-conserved region. Phylogenetic analysis indicated that CiMADS9 belongs to the AGL15 group of the MADS-box gene family. Quantitative reverse transcription polymerase chain reaction analysis indicated that the expression levels in reproductive organs(i.e.,flowers and young fruits) were considerably higher than in vegetative tissues(i.e.,leaves and branches). The highest expression levels were observed in male flowers. An overexpression vector for CiMADS9 was constructed and the gene was inserted into the Arabidopsis thaliana genome. CiMADS9 expression was confirmed in all transgenic lines. Compared with wild-type plants,transgenic A. thaliana plants overexpressing CiMADS9 exhibited delayed flowering and an increased number of leaves.