Sugar and Hormone Dynamics and the Expression Profiles of SUT/SUC and SWEET Sugar Transporters during Flower Development in Petunia axillaris

Flowering is the first committed step of plant sexual reproduction. While the developing flower is a strong sink requiring large quantity of sugars from photosynthetic source tissues, this process is under-temper-spatially controlled via hormone signaling pathway and nutrient availability. Sugar transporters SUT/SUC and SWEET mediate sugars movement across membranes and play a significant role in various physiological processes, including reproductive organ development. In Petunia axillaris, a model ornamental plant, 5 SUT/SUC and 36 SWEET genes are identified in the current version of the genome. Analysis of their gene structure and chromosomal locations reveal that SWEET family is moderately expanded. Most of the transporter genes are abundantly expressed in the flower than in other organs. During the five flower developmental stages, transcript levels of PaSUT1, PaSUT3, PaSWEET13c, PaSWEET9a, PaSWEET1d, PaSWEET5a and PaSWEET14a increase with the maturation of the flower and reach their maximum in the fully open flowers. PaSWEET9c, the nectar-specific PhNEC1 orthologous, is expressed in matured and fully opened flowers. Moreover, determination of sugar concentrations and phytohormone dynamics in flowers at the five developmental stages shows that glucose is the predominant form of sugar in young flowers at the early stage but depletes at the later stage, whereas sucrose accumulates only in maturated flowers prior to the corolla opening. On the other hand, GA3 content and to a less extent IAA and zeatin decreases with the flower development; however, JA, SA and ABA display a remarkable peak at mid- or later flower developmental stage.

Morphological characterization of sympatric and allopatric populations of Petunia axillaris and P. exserta (Solanaceae)

Floral morphological traits are frequently used to identify species, including those that are closely related and show low genetic diversity, and floral shape and colour are known to play an important role in diversification and species isolation. Floral morphology in Petunia (Solanaceae) is considered a driver of diversification because of its association with pollinators. Here, flower morphology was characterized through morphometric analyses and floral pigments. Our main aim was to determine corolla shape in populations of Petunia axillaris and P. exserta and their natural hybrids and how floral display, size and colour are involved in pollinator attraction. In addition, we investigated floral pigments in P. exserta and different hybrid classes. The results from morphometric analyses revealed that each species has a specific floral shape, independent of the collection site. By contrast, in two contact zones, a mosaic of floral phenotypes was observed with some hybrid classes based on corolla colour being placed close to P. exserta. The results suggest that several generations of hybrids or backcrossing could have given rise to this floral diversity in contact zones.

Morphological and genetic characterization in putative hybrid zones of Petunia axillaris subsp. axillaris and subsp. parodii (Solanaceae)

Petunia axillaris subsp. axillaris and P. axillaris subsp. parodii (Solanaceae) are closely related taxa primarily distinguished by their geographical distribution and floral morphology. Both are found in the southern South American Pampas ecoregion, with the latter also occurring in the Chaco ecoregion; in the Pampas, taxa occupying adjacent areas and intermediary morphologies have been observed. Here, we explored morphological traits and genetic polymorphisms to test the occurrence of hybrid zones between these taxa along the Negro River (Uruguay) and southern Brazil. Morphological data showed variation among the groups, although they could have some overlap. Genetic data also support the differences between them and hybrid zones. These findings suggest that the divergence between P. axillaris subspecies occurred with occasional hybridization in their contact zones.

Palynological Studies on Ten Species of Angiosperms from Nepal

Palynological studies on ten species of angiosperms family namely Hibiscus rosa- sinensis L.(Malvaceae), Lilium candidum L. (Liliaceae), Petunia axillaris (Lam.) B.S.P.(Solanaceae) and seven species from family asteraceae namely Artemisia indica Willd., Aster ageratoides Kitam., Calendula offcinalis L., Cerpis japonica L. (Benth.), Sonchus asper (L.) Hill, Tagetus patula L., and Taraxicum officinale F.H.Wigg. was carried out. Result obtained from this investigation showed that pollen shape is spheroidal in Artemisia indica, Aster ageratoides, Calendula offcinalis, Hibiscus rosa- sinensis and P. axillaris; elliptical in L. candidum, hexagonal in S. asper and pentagonal in T. officinale; tricolpater in C.japonica. Pollen aperture is porate in all except in L.candidum where it is elliptic. Pollen wall is echinate in H.rosa-sinensis, A.ageratoides, T. patula; spinulate in P. axillaries, T. officinale, S. asper, C. japonica, C. officinalis and T. officinale and smooth in L. candidum. The general appearance of the pollen grain is circular in P. axillaries but longer than wide in L.candidum. The circular, echinate, large and triporate pollens seem to be primitive ones and spharoidal, hexaporate features have been regarded as comparatively advanced ones. Polyporate pollens are considered to be secondarily derived. The nature of the pollen grain in these species could be evolutionary significance. The similarities in structure of the pollen grain showed the inter- species relationships among the species and that’s why put in same family while the differences in structures showed reasons for them to exist as distinct species. Only one species namely L.candidum from monocot family (Liliaceae) included in this study. Int. J. Appl. Sci. Biotechnol. Vol 5(3): 361-365

CARACTERÍSTICAS ESTRUCTURALES Y FISIOLÓGICAS DE Petunia axillaris RELACIONADAS CON SU BAJA SENSIBILIDAD A GLIFOSATO

RESUMENLa utilización repetida de glifosato como herbicida, entre otros aspectos, aumenta la frecuencia de individuos con baja sensibilidad al mismo. Entre los numerosos casos reportados de especies de malezas que han presentado algún inconveniente para su adecuado manejo se encuentra Petunia axillaris. En este trabajo se evalúa su sensibilidad y se estudian posibles mecanismos involucrados. Se analizó la retención, absorción y translocación con herbicida radiomarcado, así como también la modificación estructural producida por la aplicación del herbicida. Los análisis comprueban que Petunia axillaris es una especie tolerante a glifosato, no mostrando inhibición de la ruta metabólica del ácido shikímico. La menor sensibilidad al herbicida podría estar relacionada con una menor retención foliar de glifosato y un mayor tiempo de absorción; lo cual retarda el ingreso y movimiento del herbicida. Desde el punto de vista estructural se afecta el desarrollo del eje principal, mateniendo sin embargo una elevada producción de flores y semillas. Petunia axillaris muestra una combinación de características morfológicas-estructurales y fisiológicas que determinan su ventaja adaptativa para permanecer y aumentar su población en sistemas con uso intensivo de glifosato.