Ripe pepper (Capsicum sp.) fruits can display a range of colours from white to deep red. To understand better the regulatory mechanisms of the carotenoid biosynthetic pathways that underlie these ripening colours, Capsicum varieties that show seven different fully ripe colour types were analysed. The levels and composition of the carotenoid accumulation in these samples at different stages of ripening were measured, and the resulting data were analysed in conjunction with the expression patterns of the carotenoid biosynthetic genes. It was found that red peppers accumulate increasing levels of total carotenoids during ripening, whereas non-red peppers accumulate lower levels of total carotenoids of varying composition. The expression levels of the phytoene synthase, phytoene desaturase, and capsanthin-capsorubin synthase (Ccs) genes are high in peppers with high levels of total carotenoid, whereas one or two of these genes are not expressed in peppers with lower levels of total carotenoid. Surprisingly, it was found that the Ccs gene is present in two Capsicum varieties whose ripe colour is yellow. This gene has never previously been shown to be present in yellow peppers. Sequence analyses of the Ccs gene further revealed two structural mutations in yellow peppers that may result in either a premature stop-codon or a frame-shift. Taken together with the fact that the Ccs transcript is not detectable in yellow peppers, our current results suggest that nonsense-mediated transcriptional gene silencing of Ccs and not the deletion of this gene is responsible for yellow ripening in Capsicum.

The MYB transcription factors play important roles in the regulation of many secondary metabolites at the transcriptional level. We evaluated the possible roles of the Arabidopsis R2R3-MYB transcription factors in flavonoid biosynthesis because they are induced by UV-B irradiation but their associated phenotypes are largely unexplored. We isolated their genes by RACE-PCR, and performed transgenic approach and metabolite analyses in lettuce (Lactuca sativa). We found that one member of this protein family, AtMYB60, inhibits anthocyanin biosynthesis in the lettuce plant. Wild-type lettuce normally accumulates anthocyanin, predominantly cyanidin and traces of delphinidin, and develops a red pigmentation. However, the production and accumulation of anthocyanin pigments in AtMYB60-overexpressing lettuce was inhibited. Using RT-PCR analysis, we also identified the complete absence or reduction of dihydroflavonol 4-reductase (DFR) transcripts in At-MYB60-overexpressing lettuce (AtMYB60-117 and AtMYB60-112 lines). The correlation between the overexpression of AtMYB60 and the inhibition of anthocyanin accumulation suggests that the transcription factorAtMYB60 controls anthocyanin biosynthesis in the lettuce leaf. Clarification of the roles of the AtMYB60 transcription factor will facilitate further studies and provide genetic tools to better understand the regulation in plants of the genes controlled by the MYB-type transcription factors. Furthermore, the characterization of AtMYB60 has implications for the development of new varieties of lettuce and other commercially important plants with metabolic engineering approaches.

Molecular analysis of gene expression differences between green and red lettuce leaves was performed using the SSH method. BlastX comparisons of subtractive expressed sequence tags (ESTs) indicated that 7.6% of clones encoded enzymes involved in secondary metabolism. Such clones had a particularly high abundance of flavonoid-metabolism proteins (6.5%). Following SSH, 566 clones were rescreened for differential gene expression using dot-blot hybridization. Of these, 53 were found to overexpressed during red coloration. The up-regulated expression of six genes was confirmed by Northern blot analyses. The expression of chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and dihydroflavonol 4-reductase (DFR) genes showed a positive correlation with anthocyanin accumulation in UV-B-irradiated lettuce leaves; flavonoid 3',5'-hydroxylase (F3',5'H) and anthocyanidin synthase (ANS) were expressed continuously in both samples. These results indicated that the genes CHS, F3H, and DFR coincided with increases in anthocyanin accumulation during the red coloration of lettuce leaves. This study show a relationship between red coloration and the expression of up-regulated genes in lettuce. The subtractive cDNA library and EST database described in this study represent a valuable resource for further research for secondary metabolism in the vegetable crops.

In plants ascorbic acid (AsA) is a strong antioxidant or reductant that can be converted to dehydroascorbate (DHA) by oxidation. DHA, a very short-lived chemical, can either be hydrolyzed irreversibly to 2,3-diketogulonic acid or recycled to AsA by dehydroascorbate reductase (DHAR). DHAR cDNA, isolated from sesame hairy roots, was inserted into two plant expression vector systems with the CaMV35S promoter (CaMV35S::DHAR) and a potato tuber-specific promoter, Patatin (Patatin::DHAR). Southern and northern blot hybridization analyses indicated that DHAR cDNA was successfully integrated into the potato genome and actively transcribed. High levels of sesame DHAR transcript and DHAR enzyme activity were determined, by the Patatin promoter, in regenerated potato tubers, but their levels in leaves were very low. In contrast, much higher amounts of transcript were accumulated in the leaves of CaMV35S::DHAR regenerants than in the tubers while the activity of DHAR enzyme was higher in the latter. AsA content in the tubers of Patatin::DHAR transgenic lines was also increased (1.1. to 1.3-fold) cor~pared with that of non-transgenic plants. However, this was not true for the transgenic leaves. In contrast, the CaMV35~ promoter was associated with AsA accumulations in both the tubers (up to 1.6-fold) and the leaves (up to 1.5-fold). Howevel. more detailed analyses indicated that this increased enzyme activity was not always accompanied by an elevation in AsA .c(~ntent from transgenic plants. This suggests that other factors may limit the accumulation of vitamin C via ascorbaterecycling; in transgenic potato plants.

Abstract. Gastrodia elata Blume (GEB) is a traditional herbal plant that has been used in Asian countries for centuries as an anticonvulsant, analgesic, and also as a sedative for treating general paralysis, epilepsy, vertigo, and tetanus. Although numerous reports have addressed the effects of GEB against degenerative diseases, no previous study has examined the possible gastroprotective effects of GEB. Here, we examined the effects of pretreatment with GEB (0.02 ml/g, p.o.) in a mouse water immersion restraint (WIR) stressinduced gastric lesion model. Our results revealed that mice pretreated with GEB had significantly fewer gastric lesions than their respective controls. Moreover, GEB-treated mice showed significant decreases in serum and gastric nitric oxide (NO) levels to 50 and 28%, respectively. To examine one possible mechanism underlying this effect, we used reverse transcription-polymerase chain reaction (RT-PCR) to examine NOS mRNA expression in gastric lesion tissues. Our results revealed that the mRNA expression of inducible nitric oxide synthase (iNOS) was reduced by ~50% in GEB-pretreated mice versus the controls, whereas the mRNA expression levels of endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) remained unchanged. These findings collectively suggest that GEB significantly protects the gastric mucosa against WIR-induced gastric damage, at least in part by decreasing NO levels via suppression of iNOS mRNA expression.