Maintaining quality and bioactive compounds of broccoli by combined treatment with 1-methylcyclopropene and 6-benzylaminopurine.

BACKGROUND: Broccoli deteriorates very quickly after harvest at ambient temperature due to the loss of green colour and the consequent yellowing of florets. To search for an effective method to control quality deterioration, the effect of 1-methylcyclopropene (1-MCP) combined with 6-benzylaminopurine (6-BA) treatment on visual quality, antioxidant enzymes and bioactive compounds in broccoli florets were investigated. RESULTS: A combined treatment of 2.5 µL L⁻¹ 1-MCP and 200 mg L⁻¹ 6-BA significantly reduced the increase of lightness (L*) value, and retained a high level for the hue value (H) and chlorophyll content. Superoxide dismutase, ascobate peroxidase and catalase activities increased while the activity of peroxidase decreased during storage in treated samples in comparison with the controls. The combined treatment enhanced the biosynthesis of glucosinolate and the formation of the anticarcinogen sulforaphane, which improved the health benefit of broccoli. CONCLUSION: These results indicate that a combined treatment of 1-MCP and 6-BA could be a good candidate for maintaining the visual quality and enhancing the nutritional value in broccoli during storage at 15 °C.

Molecular cloning and functional analysis of a novel 6&1-FEH from wheat (Triticum aestivum L.) preferentially degrading small graminans like bifurcose.

Like barley and other cereals, wheat (Triticum aestivum L.) accumulates branched graminan-type fructans containing both beta-(2,1) and beta-(2,6) fructosyl linkages, mainly with a quite low degree of polymerization (DP). 1&6-kestotetraose (bifurcose) is the major fructan oligosaccharide accumulating in crown tissues and leaves of cereals exposed to chilling. The fructan exohydrolase (FEH) cDNAs 1-FEH w1 and w2 were previously cloned from wheat crowns sampled in mid-November. Here, we report the cloning and functional analysis of another FEH cDNA from a mid-November wheat crown cDNA library. The cDNA encodes a long open reading frame (ORF) of 595 amino acids. Like other FEHs, it has a low iso-electric point (5.2) and it groups together with cell-wall type invertases and not with vacuolar invertases. The deduced amino acid sequence shows 67% identity to wheat 1-FEH w1 and w2. Functional characterization of the recombinant proteins in Pichia pastoris demonstrated that the recombinant enzyme had FEH activity towards the pure compounds 1-kestose, 6-kestose, 1,1-nystose and 1,1,1-kestopentaose. However, when incubated with its putative natural substrates (a mixture of low DP graminans from wheat crowns), it was shown that 1&6-kestotetraose (bifurcose) was preferentially removed from the graminan mixture. High DP wheat graminan and bacterial levan were only poor substrates. No hydrolase activities could be detected towards sucrose and high DP inulin, convincingly demonstrating that the enzyme is not a classic invertase or 1-FEH. The enzyme was termed 6&1-FEH w1. Northern blot analyses showed that 6&1-FEH w1 was expressed in crown tissue from autumn through winter under snow, while the expression levels in leaves were minimal or not detectable. The results strongly suggest that this unique FEH might play an important role in the degradation of branched, low DP wheat graminan (like bifurcose) in wheat crowns in the high fructan content season.

Exogenous ethylene influences flower opening of cut roses (Rosa hybrida) by regulating the genes encoding ethylene biosynthesis enzymes.

The purpose of this paper is to investigate the differential responses of flower opening to ethylene in two cut rose cultivars, 'Samantha', whose opening process is promoted, and 'Kardinal', whose opening process is inhibited by ethylene. Ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) synthase and oxidase activities were determined first. After ethylene treatment, ethylene production, ACC synthase (ACS) and ACC oxidase (ACO) activities in petals increased and peaked at the earlier stage (stage 3) in 'Samantha', and they were much more dramatically enhanced and peaked at the later stage (stage 4) in 'Kardinal' than control during vasing. cDNA fragments of three Rh-ACSs and one Rh-ACO genes were cloned and designated as Rh-ACS1, Rh-ACS2, Rh-ACS3 and Rh-ACO1 respectively. Northern blotting analysis revealed that, among three genes of ACS, ethylene-in- duced expression patterns of Rh-ACS3 gene corresponded to ACS activity and ethylene production in both cultivars. A more dramatic accumulation of Rh-ACS3 mRNA was induced by ethylene in 'Kardinal' than that of 'Samantha'. As an ethylene action inhibitor, STS at concentration of 0.2 mmol/L generally inhibited the expression of Rh-ACSs and Rh-ACO in both cultivars, although it induced the expression of Rh-ACS3 transiently in 'Kardinal'. Our results suggests that 'Kardinal' is more sensitive to ethylene than 'Samantha'; and the changes of Rh-ACS3 expression caused by ethylene might be related to the acceleration of flower opening in 'Samantha' and the inhibition in 'Kardinal'. Additional results indicated that three Rh-ACSs genes were differentially associated with flower opening and senescence as well as wounding

[Ecdysone 20-monooxygenase activity of cytochrome P450 in plants and cell culture of Ajuga reptans L]. / Ekdizon-20-monooksigenaznaia aktivnost' tsitochroma P450 v rasteniiakh i kul'ture kletok Ajuga reptans L.

The concentration of cytochrome P450 and ecdysone 20-monooxygenase activity in plants and callus cell culture of the bugleweed Ajuga reptans L. were determined. The maximal ecdysone 20-monooxygenase activity of cytochrome P450 was found in vegetative rosettes of intact plants. During the stage of flowering, the ecdysone 20-monooxygenase activity of cytochrome P450 in plant leaves was higher than in other organs. It was demonstrated that the content of ecdysteroids in callus cell culture is higher than in the intact plant with concurrent retention of a high ecdysone-20-monooxygenase activity.

Are there associations between grain-filling rate and photosynthesis in the flag leaves of field-grown rice?

Rate of grain filling in terms of dry mass accumulated per panicle per day was measured in field-grown rice in the dry season in the Philippines and compared to rates of light-saturated photosynthesis per unit leaf area (P(max)) measured at 350 micro l l(-1) CO(2) for 21 d after flowering. Five new plant type (tropical japonica) varieties (NPT) and one indica variety (IR72) were used and these gave some variation in rates and patterns of grain filling. A rapid grain-filling phase (RGFP) occurred approximately 10 d after flowering in most varieties. There was no consistent relationship in any variety between the rate of grain-filling and P(max) and chlorophyll content, both of which remained mostly unchanged throughout grain filling. Significant declines in the amount of total leaf protein and ribulose bisphosphate carboxylase-oxygenase (Rubisco) occurred, but these did not occur at the same time as the RGFP in all varieties. A decrease in the ratio of chlorophyll a/b preceded these changes and a transient rise in chlorophyll content was also observed in four varieties at this time. There was no significant change in leaf non-structural carbohydrate content during or following the RGFP. It is concluded that the decline in Rubisco and protein content in NPT was not reflected in photosynthetic activity. Hence in these field experiments Rubisco accumulated to a level in excess of photosynthetic requirements, serving as a store of nitrogen for grain filling.