Molecular aspects of zygotic embryogenesis in sunflower (Helianthus annuus L.): correlation of positive histone marks with HaWUS expression and putative link HaWUS/HaL1L

Main conclusion The link HaWUS/HaL1L, the opposite transcriptional behavior, and the decrease/increase in positive histone marks bond to both genes suggest an inhibitory effect of WUS on HaL1L in sunflower zygotic embryos. In Arabidopsis, a group of transcription factors implicated in the earliest events of embryogenesis is the WUSCHELRELATED HOMEOBOX (WOX) protein family including WUSCHEL (WUS) and other 14 WOX protein, some of which contain a conserved WUS-box domain in addition to the homeodomain. WUS transcripts appear very early in embryogenesis, at the 16-cell embryo stage, but gradually become restricted to the center of the developing shoot apical meristem (SAM) primordium and continues to be expressed in cells of the niche/organizing center of SAM and floral meristems to maintain stem cell population. Moreover, WUS has decisive roles in the embryonic program presumably promoting the vegetative-to-embryonic transition and/or maintaining the identity of the embryonic stem cells. However, data on the direct interaction between WUS and key genes for seed development (as LEC1 and L1L) are not collected. The novelty of this report consists in the characterization of Helianthus annuus WUS (HaWUS) gene and in its analysis regarding the pattern of the methylated lysine 4 (K4) of the Histone H3 and of the acetylated histone H3 during the zygotic embryo development. Also, a parallel investigation was performed for HaL1L gene since two copies of the WUS-binding site (WUSATA), previously identified on HaL1L nucleotide sequence, were able to be bound by the HaWUS recombinant protein suggesting a not described effect of HaWUS on HaL1L transcription

Molecular cloning, phylogenetic analysis, and expression patterns of LATERAL SUPPRESSOR-LIKE and REGULATOR OF AXILLARY MERISTEM FORMATION-LIKE genes in sunflower (Helianthus annuus L.)

The wild sunflower (Helianthus annuus) plants develop a highly branched form with numerous small flowering heads. The origin of a no branched sunflower, producing a single large head, has been a key event in the domestication process of this species. The interaction between hormonal factors and several genes organizes the initiation and outgrowth of axillary meristems (AMs). From sunflower, we have isolated two genes putatively involved in this process, LATERAL SUPPRESSOR (LS)-LIKE (Ha-LSL) and REGULATOR OF AXILLARY MERISTEM FORMATION (ROX)-LIKE (Ha-ROXL), encoding for a GRAS and a bHLH transcription factor (TF), respectively. Typical amino acid residues and phylogenetic analyses suggest that Ha-LSL and Ha-ROXL are the orthologs of the branching regulator LS and ROX/LAX1, involved in the growth habit of both dicot and monocot species. qRT-PCR analyses revealed a high accumulation of Ha-LSL transcripts in roots, vegetative shoots, and inflorescence shoots. By contrast, in internodal stems and young leaves, a lower amount of Ha-LSL transcripts was observed. A comparison of transcription patterns between Ha-LSL and Ha-ROXL revealed some analogies but also remarkable differences; in fact, the gene Ha-ROXL displayed a low expression level in all organs analyzed. In situ hybridization (ISH) analysis showed that Ha-ROXL transcription was strongly restricted to a small domain within the boundary zone separating the shoot apical meristem (SAM) and the leaf primordia and in restricted regions of the inflorescence meristem, beforehand the separation of floral bracts from disc flower primordia. These results suggested that Ha-ROXL may be involved to establish a cell niche for the initiation of AMs as well as flower primordia. The accumulation of Ha-LSL transcripts was not restricted to the boundary zones in vegetative and inflorescence shoots, but the mRNA activity was expanded in other cellular domains of primary shoot apical meristem as well as AMs. In addition, Ha-LSL transcript accumulation was also detected in leaves and floral primordia at early stages of development. These results were corroborated by qRT-PCR analyses that evidenced high levels of Ha-LSL transcripts in very young leaves and disc flowers, suggesting a role of Ha-LSL for the early outgrowth of lateral primordia

Transposon-dependent induction of Vincent van Gogh's sunflowers: Exceptions revealed.

The radiate sunflower inflorescence is composed by zygomorphic ray flowers and actinomorphic disk flowers. Studies performed on mutants identify HaCYC2c, a CYCLOIDEA (CYC)-like gene, as one of the key players controlling flower symmetry in sunflower. turf and tub mutants are characterized by a shift from zygomorphic to actinomorphic ray flowers, caused by insertion of transposable elements (TEs) in HaCYC2c gene. In dbl or Chry mutants, an insertion upstream the coding region of HaCYC2c causes the ectopic expression of the gene and the shift from actinomorphic to zygomorphic disk flowers. We focused on Chry2 mutant: a 1034 bp insertion placed 558 bp before the start codon of HaCYC2c was identified. The insertion is a truncated version of a CACTA TE. Unexpectedly, phenotypic and genetic co-segregation analysis in F2 and F3 progenies derived from the crosses Chry2 × turf and turf × Chry2 demonstrated that CACTA insertion is not always sufficient to alter the expression of HaCYC2c gene and generate Chry2 phenotype. F3 plants homozygous for the CACTA insertion displayed either HaCYC2c transcription pattern identical to wild-type plants or a normal heterogamous inflorescence. Stated these results, we conclude that a much more complex regulatory system stays behind the Chry2 phenotype

Description of 90 inbred lines of castor plant (Ricinus communis L.)

The research describes the field comparison of 90 inbred lines of castor plant derived from both selected and wild germplasm. It was carried out in central-western Italy. An important aim of this work was to describe each inbred line based on 19 morphological traits concerning stem, leaves, racemes and capsules and then to suggest a list of descriptors to International Union for the Protection of New Varieties of Plants as to conduct the Distinctness, Uniformity and Stability test also on the castor plant. The plants in the field were grown at wide distances to avoid competition and enable observation of the growth habit, particularly the specific capacity of branching. An additional characterization of the inbred lines was obtained measuring 7 quantitative traits related to main stem and first raceme; the number of racemes per plant was used to quantify the plant branching. The results allowed distinguishing almost all the genotypes using only the morphological traits. Nectaries at the node, emergences on the stem and petioles, colour of nectaries on petiole resulted important plant descriptors. The two pairs of inbred lines (Tor87#9 vs. Tor87#83 and Pod87#255Hy2 vs. Rot95#55-23) were distinguished thanks to the quantitative traits. Based on the morphological traits, two UPGMA dendrograms, one for the dwarf and one for the normal genotypes, were characterized and the resulting clusters better explained the relationships among the various inbred lines. Six genotypes (Pod87#389, Tor87#81A, Tor87#220B, Tor87#287, Tor87#287Hy, and Liba21) resulted unable to flower in the field; in these inbred lines the induction to flower is particularly influenced by the environmental growth conditions. Regarding the branching ability, the strong apical dominance of two inbred lines (Pod94#31-2 and Pod93#211) obtained from previous breeding programs was confirmed and it was possible to detect other interesting genotypes (Pod87#287A, Pod87#287B, Tor86#67). The several inbred lines described herein showed a wide range of phenotypes that might be useful in various fields of research.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Modulated gene expression during the cold acclimation process in tolerant and sensitive clones of cultivar Leccino (Olea europaea L.)

The plants are constantly exposed to environmental changes that need to be addressed with appropriate modifications of gene expression. The genetic approach to the study of the response to biotic and abiotic stresses is of great importance in plants, for the identification of the genes involved and their activation mechanisms. In our work, we have characterized the expression of some genes induced during the acclimation under low temperatures in plants of 'Olea europaea' L., by isolating DNA sequences differentially expressed in a cold tolerant clone of Leccino cultivar by using the suppression subtractive hybridisation (SSH). The sequences obtained were analysed by sequencing. Some sequences of the libraries and from orthologous genes expressed in various abiotic/biotic stress treatments, were labelled and used as probes for slot blot hybridization with total RNAs extracted from cold sensitive and tolerant Leccino clones treated with decreasing temperatures down to -10 degreesC, thus mimicking a process of cold acclimation. Six genes were found to be of interest for the adaptation to cold stress, whose expression is differentially modulated in the two clones. The most important result was in a bimodal response during the acclimation phases, the causes of which have been discussed

Overexpression of L-galactono-1,4-lactone dehydrogenase (L-GalLDH) gene correlates with increased ascorbate concentration and reduced browning in leaves of Lactuca sativa L. after cutting

Ascorbic acid (AA) is one of the most powerful natural antioxidant able to prevent enzymatic browning after exogenous treatment of minimally-processed products. The specific mechanism by which AA prevents enzymatic browning remains still debated and a direct effect of endogenous AA stimulation and browning has never been studied. The manipulation of AA pathway is a promising approach to study the biochemicalmechanismbywhichAAacts as an antibrowning agent. In this work, cDNA of L-galactono-1,4-lactone dehydrogenase (L-GalLDH), one of the key gene of the Smirnoff–Wheeler’s branch of AA biosynthetic pathway, was isolated and overexpressed in lettuce (Lactuca sativa L. cv ‘Iceberg’), a species highly prone to browning. The hypothesis that the overexpression of L-GalLDH translates to AA accumulation and reduces the browning phenomena in lettuce leaves after cutting was tested. Our results indicate that transgenic lettuce plants, showing about 19-fold overexpression of L-GalLDHas compared towild type, had about?30 % of AA concentration in mature leaves. Transgenic plants exhibited reduced browning over the leaves, even 10 day after cutting, as demonstrated by higher values of luminosity (L*) and higher values of greenness (a*) compared to control plants. Overall, these findings provide a first evidence of the role of endogenous AA as browning-preventing agent. The obtainment of T2 transgenic lettuce plants is a promising first step to further determine the specificmechanismbywhichAA acts as an anti-browning preservative