Submitted to: Genetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2005
Publication Date: 7/1/2005
Citation: Carvalho, C.H., Boddu, J., Zehr, U.B., Axtell, J.D., Pedersen, J.F., Chopra, S. 2005. Genetic and molecular characterization of candystripe1 transposition events in sorghum. Genetica. Volume 124, Pages 201-212. Interpretive Summary: Sorghum is an important grain and forage crop because of its unusual tolerance to hot and dry environments. Thus, sorghum has been identified as a key plant species for the comparative analysis of grass genomes, and as a source of beneficial genes for agriculture. Trait characterization at the genetic and physiological level can be enhanced by the availability of transposon tagged mutations and thus transposon mutagenesis can be one of the successful genetic tools of isolating as well as functional characterization of genes in sorghum. However, until recently, no active transposable element was known in sorghum. In this study, activity of the transposable element Candystripe1 (Cs1) was assayed by characterization of new mutations in sorghum. Transposition frequency of Cs1 was assayed by using the mutable y1-cs allele that carries this transposon. Germinal excisions of the Cs1 give rise to full red headed plants. We used the Y1-regulated flavonoid pigmentation as a marker to genetically link the restriction fragment length polymorphism associated with excisions of the Cs1 from y1-cs. Newly isolated mutant phenotypes were analyzed by restriction fragment length polymorphism for the Cs1 transposon as a molecular tag to establish their linkage with the transposon insertions.
Technical Abstract: In sorghum, the Candystripe1 (Cs1) transposable element causes a variegated pericarp phenotype due to its excision activity from the y1 (yellow seed1) locus. The Y1 is a transcription regulator which is required for the biosynthesis of red 3-deoxyflavonoid pigments. Somatic variability in the transposition behavior of Cs1 was observed via biochemical analysis of 3-deoxyflavonoids in the leaf tissues of the Y1-cs alleles. Using somatic excisions of Cs1 as a tool, we establish that the Cs1 is active in young seedlings and the y1 locus is also functional in these tissues. Several somatic and germinal excision events were characterized and sequence analysis of independent events predominantly showed 2-bp footprints. Further, with the goal of understanding the properties of Cs1 that would facilitate the development of a transposon tagging system in sorghum, germinal excisions of Cs1 from y1 were used as a marker. Transposition of Cs1 was followed by characterization of putative insertion events. Genetic linkage between mutant phenotypes and the co-segregating restriction fragments of Cs1 provided additional evidence that Cs1 is an active transposable element in sorghum.