Generation of Phenylpropanoid Pathway-Derived Volatiles in Transgenic Plants: Rose Alcohol Acetyltransferase Produces Phenylethyl Acetate and Benzyl Acetate in Petunia Flowers

Esters are important contributors to the aroma of numerous flowers and fruits. Acetate esters such as geranyl acetate, phenylethyl acetate and benzyl acetate are generated as a result of the action of alcohol acetyltransferases (AATs). Numerous homologous AATs from various plants have been characterized using in-vitro assays. To study the function of rose alcohol acetyltransferase (RhAAT) in planta , we generated transgenic petunia plants expressing the rose gene under the control of a CaMV-35S promoter. Although the preferred substrate of RhAAT in vitro is geraniol, in transgenic petunia flowers, it used phenylethyl alcohol and benzyl alcohol to produce the corresponding acetate esters, not generated by control flowers. The level of benzyl alcohol emitted by the flowers of different transgenic lines was ca. three times higher than that of phenylethyl alcohol, which corresponded to the ratio between the respective products, i.e. ca. three times more benzyl acetate than phenylethyl acetate. Feeding of transgenic petunia tissues with geraniol or octanol led to the production of their respective acetates, suggesting the dependence of volatile production on substrate availability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43457/1/11103_2005_Article_4924.pd

Effects of cultivation practices on the nutritional value of crops : Wiki

This document was written for a Wageningen UR Knowledge Share (WURKS) programme in 2018. The aim of WURKS programmes is to keep educational content of the agronomic sector up to date and is financed by the Dutch Ministry of Agriculture, Nature and Food Quality (LNV). This specific program is targeted at “Tuin- en Akkerbouw” students at applied Universities (HBO) in the Netherlands

Effects of cultivation practices on the nutritional value of crops : Wiki

This document was written for a Wageningen UR Knowledge Share (WURKS) programme in 2018. The aim of WURKS programmes is to keep educational content of the agronomic sector up to date and is financed by the Dutch Ministry of Agriculture, Nature and Food Quality (LNV). This specific program is targeted at “Tuin- en Akkerbouw” students at applied Universities (HBO) in the Netherlands

Is nitric oxide a critical key factor in ABA-induced stomatal closure?

The role of nitric oxide (NO) in abscisic acid (ABA)-induced stomatal closure is a matter of debate. We conducted experiments in Vicia faba leaves using NO gas and sodium nitroprusside (SNP), a NO-donor compound, and compared their effects to those of ABA. In epidermal strips, stomatal closure was induced by ABA but not by NO, casting doubt on the role of NO in ABA-mediated stomatal closure. Leaf discs and intact leaves showed a dual dose response to NO: stomatal aperture widened at low dosage and narrowed at high dosage. Overcoming stomatal resistance by means of high CO2 concentration ([CO2]) restored photosynthesis in ABA-treated leaf discs but not in those exposed to NO. NO inhibited photosynthesis immediately, causing an instantaneous increase in intercellular [CO2] (Ci), followed by stomatal closure. However, lowering Ci by using low ambient [CO2] showed that it was not the main factor in NO-induced stomatal closure. In intact leaves, the rate of stomatal closure in response to NO was about one order of magnitude less than after ABA application. Because of the different kinetics of photosynthesis and stomatal closure that were observed, we conclude that NO is not likely to be the key factor in ABA-induced rapid stomatal closure, but that it fine-tunes stomatal aperture via different pathways

Regulation of floral scent production in petunia revealed by targeted metabolomics

Petunia hybrida line W115 (Mitchell) has large white flowers that produce a pleasant fragrance. By applying solid phase micro extraction (SPME) techniques coupled to GC-MS analysis, volatile emission was monitored in vivo using a targeted metabolomics approach. Mature flowers released predominantly benzenoid compounds of which benzaldehyde, phenylacetaldehyde, methylbenzoate, phenylethylalcohol, iso-eugenol and benzylbenzoate were most abundant. This emission had a circadian rhythm reaching its maximum at dusk. During petal limb expansion two sesquiterpenes were emitted by the petunia flowers, tentatively identified as germacrene D and cadina-3,9-diene. In vitro analysis showed that the petal limbs and stigma were the main producers of the benzenoids and sesquiterpenes, respectively. Moreover, comparison of in vivo and in vitro analysis indicated that volatiles were not stored during periods of low emission but rather were synthesized de novo. DNA-microarray analysis revealed that genes of the pathways leading to the production of volatile benzenoids were upregulated late during the day, preceding the increase of volatile emission. RNA-gel blot analyses confirmed that the levels of phenylalanine ammonia lyase (PAL) and S-adenosyl methionine (SAM) synthase transcripts increased towards the evening. Our results suggest that the circadian production of volatile benzenoids in petunia W115 is, at least partly, regulated at the transcript level

Regulation of floral scent production in petunia revealed by targeted metabolomics

Petunia hybrida line W115 (Mitchell) has large white flowers that produce a pleasant fragrance. By applying solid phase micro extraction (SPME) techniques coupled to GC-MS analysis, volatile emission was monitored in vivo using a targeted metabolomics approach. Mature flowers released predominantly benzenoid compounds of which benzaldehyde, phenylacetaldehyde, methylbenzoate, phenylethylalcohol, iso-eugenol and benzylbenzoate were most abundant. This emission had a circadian rhythm reaching its maximum at dusk. During petal limb expansion two sesquiterpenes were emitted by the petunia flowers, tentatively identified as germacrene D and cadina-3,9-diene. In vitro analysis showed that the petal limbs and stigma were the main producers of the benzenoids and sesquiterpenes, respectively. Moreover, comparison of in vivo and in vitro analysis indicated that volatiles were not stored during periods of low emission but rather were synthesized de novo. DNA-microarray analysis revealed that genes of the pathways leading to the production of volatile benzenoids were upregulated late during the day, preceding the increase of volatile emission. RNA-gel blot analyses confirmed that the levels of phenylalanine ammonia lyase (PAL) and S-adenosyl methionine (SAM) synthase transcripts increased towards the evening. Our results suggest that the circadian production of volatile benzenoids in petunia W115 is, at least partly, regulated at the transcript level