Essential Oil Gland Number and Ultrastructure During Mentha arvensis Leaf Ontogeny

Shanker, Shyam; Ajayakumar, P. V.; Sangwan, Veena; Kumar, Sudesh; Sangwan, Rajender Singh

doi:10.1023/a:1002461101852

Cited by 33 publications

(12 citation statements)

References 14 publications

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“…4A and B) was unexpected, but very consistent over leaves. A similar pattern was reported in Mentha arvensis [22]. The decrease implies that trichomes collapsed during leaf senescence.…”

Section: Discussionsupporting

confidence: 83%

Trichome Dynamics and Artemisinin Accumulation during Development and Senescence ofArtemisia annuaLeaves

Lommen

Schenk

Bouwmeester³

et al. 2006

Planta med

103

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Artemisinin is a sesquiterpene lactone endoperoxide and an important antimalarial drug produced in Artemisia annua. To unravel the diverse processes determining artemisinin yield in A. annua crops, artemisinin accumulation during the development of individual leaves was studied in two field experiments. During the life cycle of a leaf, artemisinin was always present. Quantities were low at leaf appearance and increased steadily. In leaves studied until after senescence, maximum quantities and concentrations were achieved after the leaf had turned brown. The total quantity of possible artemisinin precursors per leaf (dihydroartemisinic acid and other upstream precursors) was highest early in the leaf cycle when the leaf was still expanding. Dihydroartemisinic acid was more abundant than the other compounds and its quantity declined during leaf development whereas that of artemisinin increased. Dihydroartemisinic acid was not converted directly into artemisinin, because on a per leaf basis the decline in molar quantity of precursors in the earliest formed leaves was not compensated for by a simultaneous increase in artemisinin. Our results suggest that a (putative) intermediate such as dihydroartemisinic acid hydroperoxide temporarily may have accumulated in considerable quantities. The number of mature, capitate trichomes on the adaxial leaf side increased after leaf appearance until the end of leaf expansion, and then decreased, probably due to collapse of trichomes. Artemisinin production thus (also) occurred when trichomes were collapsing. Later formed leaves achieved higher concentrations of artemisinin than earlier formed leaves, because of a higher trichome density and a higher capacity per trichome.

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“…4A and B) was unexpected, but very consistent over leaves. A similar pattern was reported in Mentha arvensis [22]. The decrease implies that trichomes collapsed during leaf senescence.…”

Section: Discussionsupporting

confidence: 83%

Trichome Dynamics and Artemisinin Accumulation during Development and Senescence ofArtemisia annuaLeaves

Lommen

Schenk

Bouwmeester³

et al. 2006

Planta med

103

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“…According to Lommen et al 20 GT density is highest at the maximum size of leaves, after which density decreases rapidly, suggesting the rupture over time in the older leaves. Similar decrease in the GT number in Mentha arvensis from upper expanding young, to the lower level leaves proceeding for senescence is reported 21 . Duke and Paul 19 also indicated the breakage of subcuticular sac in many mature glands releasing secondary metabolites.…”

Section: Discussionsupporting

confidence: 81%

RNAi down-regulation of cinnamate-4-hydroxylase increases artemisinin biosynthesis in Artemisia annua

Kumar¹,

Vashisth²,

Misra³

et al. 2016

Sci Rep

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Cinnamate-4-hydroxylase (C4H) converts trans-cinnamic acid (CA) to p-coumaric acid (COA) in the phenylpropanoid/lignin biosynthesis pathway. Earlier we reported increased expression of AaCYP71AV1 (an important gene of artemisinin biosynthesis pathway) caused by CA treatment in Artemisia annua. Hence, AaC4H gene was identified, cloned, characterized and silenced in A. annua with the assumption that the elevated internal CA due to knock down may increase the artemisinin yield. Accumulation of trans-cinnamic acid in the plant due to AaC4H knockdown was accompanied with the reduction of p-coumaric acid, total phenolics, anthocyanin, cinnamate-4-hydroxylase (C4H) and phenylalanine ammonia lyase (PAL) activities but increase in salicylic acid (SA) and artemisinin. Interestingly, feeding trans-cinnamic acid to the RNAi line increased the level of artemisinin along with benzoic (BA) and SA with no effect on the downstream metabolites p-coumaric acid, coniferylaldehyde and sinapaldehyde, whereas p-coumaric acid feeding increased the content of downstream coniferylaldehyde and sinapaldehyde with no effect on BA, SA, trans-cinnamic acid or artemisinin. SA is reported earlier to be inducing the artemisinin yield. This report demonstrates the link between the phenylpropanoid/lignin pathway with artemisinin pathway through SA, triggered by accumulation of trans-cinnamic acid because of the blockage at C4H.

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“…Another upregulated class of sesquiterpene synthases are those which produce caryophyllene (sequence homology E-value <10 −110 ), a sesquiterpene oil that has been found to be the main constituent of curry essential oil 13 , 14 , 16 , 20 , yielding the various medicinal properties of the leaf 19 . This supports anatomical studies which show that oil gland counts continue to increase late into leaf development 47 . The upregulation of this class of enzymes indicates an increase in the production of these oils during leaf development.…”

Section: Discussionsupporting

confidence: 89%

Transcriptome analysis of the curry tree (Bergera koenigii L., Rutaceae) during leaf development

Shivakumar

Johnson

Zimmer

2019

Sci Rep

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The curry tree (Bergera koenigii L.) is a widely cultivated plant used in South Asian cooking. Next-generation sequencing was used to generate the transcriptome of the curry leaf to detect changes in gene expression during leaf development, such as those genes involved in the production of oils which lend the leaf its characteristic taste, aroma, and medicinal properties. Using abundance estimation (RSEM) and differential expression analysis, genes that were significantly differentially expressed were identified. The transcriptome was annotated with BLASTx using the non-redundant (nr) protein database, and Gene Ontology (GO) terms were assigned based on the top BLAST hit using Blast2GO. Lastly, functional enrichment of the assigned GO terms was analyzed for genes that were significantly differentially expressed. Of the most enriched GO categories, pathways involved in cell wall, membrane, and lignin synthesis were found to be most upregulated in immature leaf tissue, possibly due to the growth and expansion of the leaf tissue. Terpene synthases, which synthesize monoterpenes and sesquiterpenes, which comprise much of the curry essential oil, were found to be significantly upregulated in mature leaf tissue, suggesting that oil production increases later in leaf development. Enzymes involved in pigment production were also significantly upregulated in mature leaves. The findings were based on computational estimates of gene expression from RNA-seq data, and further study is warranted to validate these results using targeted techniques, such as quantitative PCR.

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Essential Oil Gland Number and Ultrastructure During Mentha arvensis Leaf Ontogeny

Cited by 33 publications

References 14 publications

Trichome Dynamics and Artemisinin Accumulation during Development and Senescence ofArtemisia annuaLeaves

Trichome Dynamics and Artemisinin Accumulation during Development and Senescence ofArtemisia annuaLeaves

RNAi down-regulation of cinnamate-4-hydroxylase increases artemisinin biosynthesis in Artemisia annua

Transcriptome analysis of the curry tree (Bergera koenigii L., Rutaceae) during leaf development

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