Transposon Tagging of the Defective embryo and meristems Gene of Tomato

Abstract

The shoot and root apical meristems (SAMs and RAMs, respectively) of higher plants are mechanistically and structurally similar. This has led previously to the suggestion that the SAM and RAM represent modifications of a fundamentally homologous plan of organization. Despite recent interest in plant development, especially in the areas of meristem regulation, genes specifically required for the function of both the SAM and RAM have not yet been identified. Here, we report on a novel gene, Defective embryo and meristems ( Dem ), of tomato. This gene is required for the correct organization of shoot apical tissues of developing embryos, SAM development, and correct cell division patterns and meristem maintenance in roots. Dem was cloned using transposon tagging and shown to encode a novel protein of 72 kD with significant homology to YNV2, a protein of unknown function of Saccharomyces cerevisiae. Dem is expressed in root and shoot meristems and organ primordia but not in callus. The expression pattern of Dem mRNA in combination with the dem mutant phenotype suggests that Dem plays an important role within apical meristems. INTRODUCTIONIn plants, organogenesis is continuous and occurs in apices throughout the entire life cycle. This process is achieved by the action of apical meristems, which are groups of stem cells that are established early in embryogenesis and maintained in the tips of shoots and roots. Because apical meristems are almost entirely responsible for the elaboration of plant architecture, they have been a major subject of observational, experimental, and genetic studies (described in Steeves and Sussex, 1991;Meyerowitz, 1997). We are now beginning to elucidate the genes involved in meristem regulation and to understand their function (Meyerowitz, 1997).In angiosperms, the shoot apical meristem (SAM) is usually a small dome of cells that consists of a peripheral zone in which leaves are initiated and a central zone in which the peripheral zone cells are replenished. The central zone contains cells that divide slowly, whereas the peripheral zone contains cells that divide rapidly (Lyndon, 1990;Steeves and Sussex, 1991). Superimposed upon this zonation are three clonally distinct cell layers (Poethig, 1987): L1 (forming the epidermis), L2 (forming the mesoderm), and L3 (forming the pith and vascular tissue). These cell layers generate the whole shoot. The L1 and L2 layers in the SAM are maintained by anticlinal cell divisions. Occasional cell divisions occur that result in the insertion of cells derived from one layer into the adjacent layer. These cells adopt a fate appropriate to their new layer, thus suggesting that positional information, rather than cell lineage, is the major factor influencing cell fate decisions during plant development. How cells in meristems communicate with each other has not yet been determined; however, recent results indicate roles for protein trafficking (Lucas et al., 1995) and extracellular signaling (Clark et al., 1997).The root apical meristem (RAM), in contrast to ...

Intron splicing suppresses RNA silencing in Arabidopsis

“…To test the effect of introns on transgene silencing, we inserted the intron from the endogenous DEM1 gene (Keddie et al. , 1998) of Arabidopsis ( At4g33400 ) within the 5′ untranslated region (UTR) of the 35S:GFP transgene.…”

“…To test the effect of introns on transgene silencing, we inserted the intron from the endogenous DEM1 gene (Keddie et al, 1998) of Arabidopsis (At4g33400) within the 5¢ untranslated region (UTR) of the 35S:GFP transgene. Remarkably, the percentage of silenced T 1 plants was reduced from 85% without the intron to 36% with the DEM1 intron (Figure 2c,d).…”

An Efficient Approach for the Development of Locus Specific Primers in Bread Wheat (Triticum aestivum L.) and Its Application to Re-Sequencing of Genes Involved in Frost Tolerance

“…In addition, they reported that the variation in Cbf genes, which do not carry any introns, is widespread in the Triticeae [ 26 ]. This gene family is regulated by two wheat specific Ice genes under cold conditions [ 27 , 28 ]. Both Ice genes have four exons [ 29 , 30 ].…”

“…Tacr7 belongs to the group of LT genes [ 31 ]. The Dem genes have an important role in the development of apical meristems and are thereby involved in the vegetative/reproductive transition of the shoot apex [ 27 ].…”

RNA-Seq analysis reveals that multiple phytohormone biosynthesis and signal transduction pathways are reprogrammed in curled-cotyledons mutant of soybean [Glycine max (L.) Merr.]

“…In Arabidopsis , as a paradigm for dicot embryonic development, cotyledons are specified from two lateral domains at the apical end of the embryo proper at the heart stage, showing bilateral symmetry [ 2 ]. Several studies have reported cotyledon mutants in Arabidopsis [ 3 – 7 ], Antirrhinum [ 8 ], tomato [ 9 – 11 ], and other plants [ 12 ]. These mutants have been used to identify a number of orthologous gene hierarchies that are involved in cotyledon development [ 13 ].…”