The inflorescence of sunflower (Helianthus annuus L.) is heterogamous with zygomorphic ray flowers located in the outermost whorl of the head and actinomorphic disk flowers arrayed in arcs radiating from the center of the head. Two mutants with altered corolla symmetry have been described. The Chrysanthemoides (Chry) mutant is characterized by a shift from the polysymmetric corolla of disk flowers into a monosymmetric ray-like corolla. The tubular ray flower (turf) mutant is characterized by a shift from the zygomorphic corolla of ray flowers into a nearly actinomorphic tubular-like corolla. We performed a genetic analysis of turf, showing that a single nuclear recessive gene controls the trait. Furthermore, we characterized in detail the morphological floral features of Chry and turf, demonstrating that both mutations also affect the development of stamens and carpels. Most disk flowers found in the peripheral whorls of Chry heads showed drastic reduction in stamen length, as well as absence of ovules, and developed an unbranched style. By contrast, tubular-like ray flowers of turf achieved the ability to differentiate both fertile stamens and ovules. Homeotic transformations were also identified in the tubular-like ray flowers of turf, affecting both filaments and anthers that displayed petaloid-like traits. Our results point to a primary role for TURF and CHRY in the programming of the corolla symmetry and suggest a key interaction of both genes with floral organ identity genes.Résumé : L'inflorescence du tournesol (Helanthus annuus L.) est hétérogame, avec des fleurs à rayons asymétriques localisées sur le verticille le plus externe du capitule, et des fleurs tubuliformes symétriques, sur la surface du disque, arrangées selon des arcs s'irradiant du centre vers la périphérie du capitule. On a déjà décrit deux mutants dont la symétrie de la corolle est altérée. Le mutant Chrysanthémoïde (Chry) se caractérise par un déplacement de la corolle polysymétrique des fleurs du disque vers une corolle monosymétrique d'aspect ligulé. Le mutant à fleur tubuliflore (turf) se caractérise par un déplacement d'une corolle asymétrique, constituée de fleurs ligulées, vers une corolle de fleurs d'aspect tubulé presque symétrique. Les auteurs ont conduit une analyse génétique sur le turf, laquelle montre qu'un simple gène nucléique récessif contrôle ce caractère. De plus, ils ont caractérisé en détail les particularités de la morphologie florale du Chry et du turf, démontrant que les deux mutations affectent également le développement des éta-mines et des carpelles. La plupart des fleurs du disque, localisées dans les verticilles périphériques des capitules Chry, montrent une nette réduction de la longueur des étamines, ainsi qu'une absence d'ovule, et développent un style nonramifié. Par opposition, les fleurs des rayons d'aspect tubulé du turf parviennent à différencier des étamines et des carpelles fertiles. On a également identifié des transformations homéotiques dans les fleurs d'aspect tubulé des rayons du turf, qui affect...

The indeterminate inflorescence of sunflower (Helianthus annuus) is heterogamous with zygomorphic ray flowers in the outer whorl of the head and actinomorphic disc flowers arrayed in arcs radiating from the centre of the head. The Chrysanthemoides (Chry) mutant is characterised by a change of the radially symmetric corolla of tubular disc flowers into a monosymmetric ligulate-like corolla. Zygomorphy is pronounced in the disc flowers placed on the peripheral whorls of inflorescences, while the monosymmetry is less marked toward the centre of the inflorescence. Although the Chry phenotype was one of first known morphological mutants in plants, studies on the genetic control of this trait are scarce and contradictory. Our results indicate that the Chry mutation is semidominant and exclude a maternal influence. Moreover, the data gathered in F 2 , BC 1 and F 3 progenies support a genetic model involving one major locus and an unknown number of modifiers. The improved knowledge on genetic control of the Chry mutation should enhance the introduction of this trait in crossbreeding programmes designed to produce new varieties of ornamental sunflower.

The observed phenotype and the high level of auxin detected in stf plants suggest that the STF gene is necessary for the proper initiation of primordia and for the establishment of a phyllotactic pattern through control of both SAM arrangement and hormonal homeostasis.

The initiation and growth of axillary meristems are fundamental components of plant architecture. Here, we describe the mutant missing flowers (mf) of Helianthus annuus characterized by the lack of axillary shoots. Decapitation experiments and histological analysis indicate that this phenotype is the result of a defect in axillary meristem initiation. In addition to shoot branching, mutation affects floral differentiation. The indeterminate inflorescence of sunflower (capitulum) is formed of a large flat meristem which produces floret primordia in multiple spirals. In wildtype plants a bisecting crease divides each primordium in two distinct bumps that adopt different fate. The peripheral (abaxial) part of the primordium becomes a small leaf-like bract and the adaxial part becomes a flower. In the mf mutant, the formation of flowers at the axil of bracts is precluded. Histological analyses show that in floret primordia of the mutant a clear subdivision in dyads is not established. The primordia progressively bend inside and only large involucral floral bracts are developed. The results suggest that the MISSING FLOWERS gene is essential to provide or perceive an appropriate signal to the initiation of axillary meristems during both vegetative and reproductive phases.

Nitration of anthyridine-2,6-dione (I) gave 7-nitroanthyridine-2,6-dione (11). Treatment of this compound with phosphorus pentasulfide afforded 7-aminoanthyridine-2,6-dithione (111).Desulfurization of the thioderivative 111 with Raney Nickel and subsequent aromatization of 3-amino-5,lO-dihydroanthyridine (VI) in boiling nitrobenzene, gave 3-aminoanthyridine (VII) in satisfactory yield. The structure of 3-aminoanthyridine was demonstrated and its physicochemical features are not in agreement with that previously reported in literature. The preparation of 3-aminoanthyridine-5-one (XII) is also described.Previously T. Takahashi and coworkers (1) described the isolation of 3aminoanthryridine (VII) by treatment of S-amin0-2,2'-dipyridilamine hydrochloride with oxalic acid and glycerol at 130". 3-Aminoanthyridine is reported to be a colourless solid melting at 125-128". No other physicochemical data were reported by Takahashi and no structural proof was given. We recently reported the syntheses of several anthyridine derivatives (2a,b,c,d,e) and also the preparation of the parent nucleus (3) (m.p. 295.297"). The structures of these compounds were unequivocally assigned based upon chemical and physical evidence. In general, these substances are very highmelting crystalline solids, slightly soluble in the usual organic solvents. The relatively low melting point of the product isolated by Takahashi led us to repeat the reaction. However, various attempts to prepare the substance melting at 125-128" failed giving almost quantitative recovery of starting material.