Assessment of weather effect on flower morphogenesis and fruit set in mango varieties in central India

A two-year field experiment was initiated in 2017-18 and 2018-19 years simultaneously to assess temperature on flower morphogenesis stages, flower sex ratio (hermaphrodite/staminate male flower) and fruit set in monoembryonic Langra and Amrapali varieties. Different dates of flower phenological stages viz., bud, panicle, bloom and flower initiation, pea, marble, egg, and maturity of fruits were recorded. The Langra variety exhibited bud initiation after mid December whereas Amrapali variety by the end of December. The range of mean maximum / minimum temperature as 26-31/10-12 °C promoted hermaphrodite flowers per panicle by 74 per cent in Langra variety, whereas range of 27-29/11-13 °C favored by 35 per cent in Amrapali variety. A positive and significant correlation between total number of flower / panicle and flower sex ratio in both the varieties suggested that higher temperature during initial flower phenologies improved number of hermaphrodite flowers. A mean minimum temperature for producing more number of hermaphrodite flower exhibited a range of 11-14 °C under central Indian conditions. Fruit set was maximum during pea stage and decline afterwards in marble and fruit maturity stages due to sudden rise in temperature at marble stage that caused in drop down of humidity thereby resulted in fruit drop in both the varieties.

Flower morphogenesis and gametophyte fertility attest to the rare condition of gynomonoecy in Parietaria debilis (Urticaceae)

Parietaria debilis G. Forst. is gynomonoecious, which is a rare condition in the Urticaceae family and among angiosperms. Apetalous flowers of two different morph types (monoclinous, pistillate) occur in the same inflorescence and are reduced in size and in the number of whorls and of organs per whorl. The objective of this study was to compare the morphogenesis of monoclinous and pistillate flowers to determine whether the monoclinous flowers produce fertile gametophytes, and elucidate the pathways leading to the absence of stamens and to the changes in number of whorls and organs per whorl. Flower buds and flowers (non-fertilized, fertilized) were processed for surface and anatomical studies. Pollen ultrastructure and viability were determined. Inflorescences with fertilized flowers were checked for the presence and location of fruits/viable seeds. The monoclinous flower has four sepals, four stamens, and a uniovulate pseudomonomerous gynoecium. In the pistillate flower, the stamens are absent or, rarely, aborted. No petals are formed. The gynoecium is pseudomonomerous, originated as a central primordium that differentiates into two carpels, but only one develops and houses an ovule. Monoclinous and pistillate flowers produce viable seeds. Thus, our data confirmed that this species is indeed gynomonoecious.

Silencing of PhLA, a CIN-TCP gene, causes defected petal conical epidermal cell formation and results in reflexed corolla lobes in petunia

Background TCP-domain proteins, plant specific transcription factors, play important roles in various developmental processes. CIN-TCPs control leaf curvature in simple leaf species while regulate leaf complexity in compound leaf species. However, the knowledge was largely based on findings in few model species. To extend our knowledge on this group of proteins in Solanaceae species, we identified a CIN-TCP gene from petunia, and studied its functions using virus-induced gene silencing (VIGS). Results Consistently, silencing of CIN-TCPs increases complexity of tomato leaves, and enhances leaf curvature in Nicotiana benthamiana. However, in petunia (Petunia hybrida), silencing of petunia LA, a CIN-TCP, through VIGS did not obviously affect leaf shape. The silencing, however, enhanced petal curvature. The event was associated with petal expansion at the distal portion where epidermal cell size along the midribs was also increased. The enlarged epidermal cells became flattened. Although shapes of PhLA-silenced flowers largely resemble phmyb1 mutant phenotype, PhMYB1 expression was not affected when PhLA was specifically silenced. Therefore, both PhLA and PhMYB1 are required to regulate flower morphology. In corolla, PhLA and miR319 deferentially express in different regions with strong expressions in limb and tube region respectively. Conclusions In conclusion, unlike LA-like genes in tomato and N. benthamiana, PhLA plays a more defined role in flower morphogenesis, including petal curvature and epidermal cell differentiation.

Dynamics of H3K4me3 Chromatin Marks Take the Lead over H3K27me3 for Gene Regulation during Flower Morphogenesis in Arabidopsis thaliana

Plant life-long organogenesis involves sequential, time and tissue specific expression of developmental genes. This requires activities of Polycomb Group (PcG) and trithorax Group complexes, respectively responsible for repressive Histone 3 trimethylation at lysine 27 (H3K27me3) and activation-related H3K4me3. However, the genome-wide dynamics in histone modifications that occur during developmental processes have remained elusive. Here, we report the distributions of H3K27me3 and H3K4me3 along with transcriptional changes, in a developmental series including Arabidopsis leaf and three stages of flower development. We found that chromatin mark levels are highly dynamic over the time series on nearly half of all Arabidopsis genes. Moreover, during early flower morphogenesis, changes in H3K4me3 prime over changes in H3K27me3 and quantitatively correlate with transcription changes, while H3K27me3 changes occur after prolonged expression changes. Notably, early activation of PcG target genes is dominated by increases in H3K4me3 while H3K27me3 remains present at the locus. Our results reveal H3K4me3 as greater predictor over H3K27me3 for transcription dynamics, unveil unexpected chromatin mechanisms at gene activation and underline the relevance of tissue-specific temporal epigenomics.