The role of sucrose as a signaling molecule in plants was originally proposed several decades ago. However, recognition of sucrose as a true signal has been largely debated and only recently this role has been fully accepted. The best-studied cases of sucrose signaling involve metabolic processes, such as the induction of fructan or anthocyanin synthesis, but a large volume of scattered information suggests that sucrose signals may control a vast array of developmental processes along the whole life cycle of the plant. Also, wide gaps exist in our current understanding of the intracellular steps that mediate sucrose action. Sucrose concentration in plant tissues tends to be directly related to light intensity, and inversely related to temperature, and accordingly, exogenous sucrose supply often mimics the effect of high light and cold. However, many exceptions to this rule seem to occur due to interactions with other signaling pathways. In conclusion, the sucrose role as a signal molecule in plants is starting to be unveiled and much research is still needed to have a complete map of its significance in plant function.

https://www.tandfonline.com/doi/pdf/10.4161/psb.23316

Sucrose signaling in plants: A world yet to be explored

Plant secondary biosynthetic pathways are exceedingly inducible by elicitors and facilitate enhanced metabolite production using plant cell tissue and organ cultures. Elicitors can regulate large number of control points and trigger the expression of key genes with increased cellular activities at biochemical and molecular level involving signal compounds. A large number of chemical elicitors viz: jasmonic acid (JA), methyl jasmonate (MeJA), salicylic acid (SA), acetyl salicylic acid (ASA), ethylene (ET) and ethrel (Ethe), heavy metals (HM), many types of chemical compounds (natural or synthetic) and their combinations are used for elicitation studies. Cell suspensions and hairy roots are commonly used culture systems followed by adventitious roots and multiple shoots for elicitation experiments. Amongst the elicitors and concentrations used 100 µM MeJA was found optimum for secondary metabolite enhancement in majority of experiments compared to SA and JA. Elicitor treatments promoted yield enhancements starting from 1.0 to maximum of 2230-fold across plant species studied. Elicitors singly with media additives, combination of elicitors and elicitors other than signal compounds along with hormones were found beneficial for enhanced secondary metabolite production. Further, a combination of target gene over expression and elicitor treatment also supported higher secondary product yield. The present communication presents information exclusively about the use of chemical elicitors for secondary metabolites production in vitro covering approximately more than a decade of research at one place in one review. Further, this extensive appraisal will be useful for the understanding and manipulation of secondary metabolites for enhanced production in vitro.

Chemical elicitors versus secondary metabolite production in vitro using plant cell, tissue and organ cultures: recent trends and a sky eye view appraisal

The effects of yeast extract and selected polysaccharide elicitors on secondary metabolite production, particularly of anthocyanin and phenolic acid, in cell suspension cultures of Vitis vinifera were investigated. All elicitors either maintained or promoted cell growth in culture. Overall, secondary metabolite production in V. vinifera cell suspension cultures responded differently to different elicitors. Chitosan, pectin, and alginate enhanced production of anthocyanin within 13 days of culture with levels of 2.5-, 2.5-, and 2.6-fold increase, respectively, over that of control. Chitosan, alginate, and gum arabic significantly promoted accumulation of phenolic acids, particularly 3-O-glucosyl-resveratrol, in V. vinifera cultures, as well as in the culture medium. Intracellular phenolic acid production was significantly enhanced by alginate and chitosan, with 1.7- and 1.5-fold levels, respectively, of that of control. Extracellular phenolic acid production was also significantly increased in the presence of chitosan and gum arabic, with levels of 3.3- and 1.7-fold higher, respectively, than those of control. In addition, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity was enhanced in the presence of elicitors, and this was positively correlated with increased accumulation of anthocyanin in V. vinifera cell suspension cultures.

Polysaccharide elicitors enhance anthocyanin and phenolic acid accumulation in cell suspension cultures of Vitis vinifera

This study was undertaken to investigate the effects of salicylic acid (SA) and methyl jasmonate (MeJA) on anthocyanin induction, biomass accumulation, and color value (CV) indices for both pigment content (PC) and pigment production (PP) in callus cultures of Rosa hybrida cv. Pusa Ajay. A concentration-dependent response was exhibited by cultures on SA and MeJA at different concentrations individually or in combinations to Euphorbia millii medium supplemented with 204.5 mM sucrose, 2.45 μM indole butyric acid and 2.33 μM kinetin. There was positive influence on both callus biomass and anthocyanin accumulation. Treatment with 0.5 μM MeJA was most effective in inducing anthocyanin biosynthesis in callus cultures. Anthocyanin accumulation in callus cultures was enhanced with the addition of SA and MeJA, but these did not differ significantly from control for the number of days required for pigment initiation and for color intensification. Moreover, the addition of 0.5 μM MeJA alone resulted in a higher frequency of color response (97.25 %), PC (3.48 ± 0.07 CV g−1 FW), and PP (1.56 ± 0.03 CV test tube−1) over control. In contrast, the presence of higher levels of SA (400 μM) and MeJA (5.0 μM) reduced frequency of color response, as well as levels of PC and PP. MeJA did not increase biomass accumulation but promoted frequency of color response, PC and PP. Hence, it was suggested that 0.5 μM MeJA promoted anthocyanin production in rose callus cultures. Significant correlation was found between frequency of response and each of the PC (r = 0.988) and PP (r = 0.990). Furthermore, PC and PP were also highly correlated (r = 0.998).

Influence of salicylic acid and methyl jasmonate elicitation on anthocyanin production in callus cultures of Rosa hybrida L.

Gymnema sylvestre is a natural source of gymnemic acids—a group of closely related triterpenoid saponins used in the treatment of diabetes. The present study is aimed at enhancing gymnemic acid production in G. sylvestre cell suspension cultures using the signaling molecules—methyl jasmonate and salicylic acid. Methyl jasmonate yielded the maximum gymnemic acid content of 135.41 ± 0.43 mg g−1 dry cell weight (DCW), 72 h after elicitor application. Salicylic acid, on the other hand, evoked a moderate response reaching a maximum of 43.27 ± 0.80 mg g−1 DCW, 48 h after application. The results of the present study increase the possibility for commercial production of gymnemic acids on a large scale using G. sylvestre cell suspensions.

https://link.springer.com/content/pdf/10.1007%2Fs11627-014-9655-8.pdf

Gymnemic acid enhancement in the suspension cultures of Gymnema sylvestre by using the signaling molecules—methyl jasmonate and salicylic acid

The influence of varied concentrations of sucrose and ammonical (NH4+) nitrogen on in vitro induction and expression of anthocyanin pigments from Rosa hybrida cv. ‘Pusa Ajay’ was investigated. Of two explants (petal and leaf discs) selected and cultured under two different conditions (light and dark), leaf discs were found to be most suitable for callus initiation. Profuse and early callus induction was observed when leaf discs of rose were cultured under total dark conditions on solid Murashige and Skoog (MS) medium supplemented with 4.0 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D). Early pigment initiation, enhancement and maximum anthocyanin production from calluses were recorded when leaf discs were cultured on Euphorbia millii (EM) medium supplemented with 7% sucrose compared with calluses cultured at 4% sucrose concentration under 16/8 h (light/dark) photoperiod regime. Reducing the concentration of NH4+ nitrogen in the solid MS medium led to slight improvement in anthocyanin production in rose leaf calluses.

Induction of anthocyanin pigments in callus cultures of Rosa hybrida L. in response to sucrose and ammonical nitrogen levels

In vitro carotenoid pigment production in callus cultures of Calendula officinalis L. was investigated using two basal media, semi-solid versus liquid media and varied concentrations of sucrose, ammonium, and nitrate nitrogen. Of the two explants that were evaluated, floret explants were best for callus induction using Murashige and Skoog (MS) medium supplemented with 2.0 mg l−1 2,4-dichlorophenoxyacetic acid under complete darkness. Carotenoid pigment induction was significantly augmented when the sucrose concentration was increased. Low sucrose concentrations in the culture medium deferred the onset of pigment induction and reduced the overall levels of carotenoid pigments produced. The highest amount of carotenoid pigments was observed when the callus was grown on the MS medium without ammonium nitrogen. The quantity of carotenoids was slightly elevated in cultures grown on semi-solid medium than those grown in liquid medium. In vitro carotenoid production was optimized by modifying the concentration of ammonium nitrogen to nitrate nitrogen in the culture medium and enhancing the sucrose concentration.

Induction of carotenoid pigments in callus cultures of Calendula officinalis L. in response to nitrogen and sucrose levels

Mutation breeding played a pivotal role in generating genetic variation in chrysanthemum. As a result of gamma radiation large numbers of novel mutants appear in the form of chimeras that differ in flower colour, shape and size. Isolation of such types of mutated tissue is impossible through conventional techniques. Therefore, all such novel mutants appear as a result of mutation is lost every year due to lack of suitable means to isolate them through conventional propagation methods. Therefore, an effort was made to develop efficient regeneration system from ray florets of a chrysanthemum mutant in order to isolate, purify and field establish the novel mutant. The maximum survival of cultures were found when the ray florets were per-treated with mancozeb-45 (0.2%) + carbendazim (0.2%) + 8-HQC (200 mg/l) for 3 h followed by surface sterilized with HgCl2 (0.1%) for a duration of four minutes. The callus induction was maximum on Murashige and Skoog (MS) medium supplemented with BAP (4.0 mg/l) and NAA (1.0 mg/l). The maximum regeneration of microshoots (95.56%) from the ray floret induced callus was recorded on MS medium fortified with BAP (4.0 mg/l) and NAA (0.1 mg/l). MS medium supplemented with BAP (5.0 mg/l) + NAA (0.1 mg/l) + GA3 (0.2 mg/l) gave the highest microshoot proliferation (100.0%). In vitro rooting ideal (99.0%) on half-strength MS medium fortified with 0.5 mg/l NAA. The hardening of rooted plantlets was successfully achieved after 3–4 weeks of acclimatization. The isolated mutant produced flowers that were true-to-type to the original red mutant, i.e., solid mutant.

In vitro isolation of red coloured mutant from chimeric ray florets of chrysanthemum induced by gamma-ray

Connective tissue nevi of the skin are benign hamartomatous lesions consisting predominantly of one of the components of the extracellular matrix comprising of collagen, elastin or glycosaminoglycans type. Connective tissue nevi may be solitary or multiple, sporadic or inherited. Collagenomas are asymptomatic and usually occurs over upper trunk, arms, back, thighs and soles. We, hereby report a young boy with collagenoma over the scalp, a rare site.

Surendra Kumar

Papers

Influence of salicylic acid and methyl jasmonate elicitation on anthocyanin production in callus cultures of Rosa hybrida L.

Induction of anthocyanin pigments in callus cultures of Rosa hybrida L. in response to sucrose and ammonical nitrogen levels

Induction of carotenoid pigments in callus cultures of Calendula officinalis L. in response to nitrogen and sucrose levels

In vitro isolation of red coloured mutant from chimeric ray florets of chrysanthemum induced by gamma-ray

Isolated collagenoma on the scalp: A rare presentation