Epigenetic regulation of photoperiodic flowering

Interplay of phytohormones and epigenetic regulation: A recipe for plant development and plasticity

Both phytohormone signaling and epigenetic mechanisms have long been known to play crucial roles in plant development and plasticity in response to ambient stimuli. Indeed, diverse signaling pathways mediated by phytohormones and epigenetic processes integrate multiple upstream signals to regulate various plant traits. Emerging evidence indicates that phytohormones and epigenetic processes interact at multiple levels. In this review, we summarize the current knowledge of the interplay between phytohormones and epigenetic processes from the perspective of phytohormone biology. We also review chemical regulators used in epigenetic studies and propose strategies for developing novel regulators using multidisciplinary approaches.

Study of genetic modifications of flower development and methylation status in phytoplasma infected Brassica (Brassica rapa L.)

BACKGROUND

The plants of B. rapa (syn. B. campestris) are the most important food crop of Pakistan for the production of cooking oil. Brassica plants infected by phytoplasma exhibit floral abnormalities including phyllody, virescence, hypertrophied sepal and aborted reproductive organs and affected flower developmental genes which reduces the yield manifold.

METHODS AND RESULTS

The expression level of flower developmental genes in healthy and phytoplasma infected brassica were compared by using semi-quantitative reverse transcription polymerase chain reaction and DNA hybridization. In infected brassica, LEAFY (LFY) gene, controlling the development and maintenance of floral organ, and directly involved in controlling the homeotic gene expression was affected, while APETALA2, regulate the production of sepals and petals, were not altered. Whereas the genes WUSCHEL, APETALA3 and AGAMOUS, were significantly down-regulated, that were responsible for the identity of shoot and central meristem, petals and stamens production, and stamens and carpels development, respectively. The GLUB gene, controlling the production of β-1,3-glucanases enzyme, was highly up-regulated. According to DNA hybridization results, AGAMOUS and APETALA3 were restricted to floral organs territories in healthy and phytoplasma infected brassica, indicating that their expression was tissue-specific. These outcomes indicated that flower abnormalities of phytoplasma infected B. rapa are linked with DNA methylation in the expression of homeotic genes regulating flower development.

CONCLUSIONS

Azacitidine act as a DNA demethylating reagent. By applying the foliar spray of azacitidine during the flower development, cells of Phytoplasma infected plants exhibits demethylation of DNA when treated with azacitidine chemical that incorporated as analogue of cytosine during the cell division stage. B. rapa showed the up-regulation of gene expression level significantly that restore the normal production of flowers, ultimately increase the oil production throughout the world.

Plant hormone signaling in flowering: An epigenetic point of view

Reproduction is one of the most important phases in an organism's lifecycle. In the case of angiosperm plants, flowering provides the major developmental transition from the vegetative to the reproductive stage, and requires genetic and epigenetic reprogramming to ensure the success of seed production. Flowering is regulated by a complex network of genes that integrate multiple environmental cues and endogenous signals so that flowering occurs at the right time; hormone regulation, signaling and homeostasis are very important in this process. Working alone or in combination, hormones are able to promote flowering by epigenetic regulation. Some plant hormones, such as gibberellins, jasmonic acid, abscisic acid and auxins, have important effects on chromatin compaction mediated by DNA methylation and histone posttranslational modifications, which hints at the role that epigenetic regulation may play in flowering through hormone action. miRNAs have been viewed as acting independently from DNA methylation and histone modification, ignoring their potential to interact with hormone signaling - including the signaling of auxins, gibberellins, ethylene, jasmonic acid, salicylic acid and others - to regulate flowering. Therefore, in this review we examine new findings about interactions between epigenetic mechanisms and key players in hormone signaling to coordinate flowering.

Stress enhances the gene expression and enzyme activity of phenylalanine ammonia-lyase and the endogenous content of salicylic acid to induce flowering in pharbitis

The involvement of salicylic acid (SA) in the regulation of stress-induced flowering in the short-day plant pharbitis (also called Japanese morning glory) Ipomoea nil (formerly Pharbitis nil) was studied. Pharbitis cv. Violet was induced to flower when grown in 1/100-strength mineral nutrient solution under non-inductive long-day conditions. All fully expanded true leaves were removed from seedlings, leaving only the cotyledons, and flowering was induced under poor-nutrition stress conditions. This indicates that cotyledons can play a role in the regulation of poor-nutrition stress-induced flowering. The expression of the pharbitis homolog of PHENYLALANINE AMMONIA-LYASE, the enzyme activity of phenylalanine ammonia-lyase (PAL; E.C. 4.3.1.5) and the content of SA in the cotyledons were all up-regulated by the stress treatment. The Violet was also induced to flower by low-temperature stress, DNA demethylation and short-day treatment. Low-temperature stress enhanced PAL activity, whereas non-stress factors such as DNA demethylation and short-day treatment decreased the activity. The PAL enzyme activity was also examined in another cultivar, Tendan, obtaining similar results to Violet. The exogenously applied SA did not induce flowering under non-stress conditions but did promote flowering under weak stress conditions in both cultivars. These results suggest that stress-induced flowering in pharbitis is induced, at least partly, by SA, and the synthesis of SA is promoted by PAL.