[Fruit-specific expression of sweet protein Brazzein in transgenic tomato plants].

The AGPL1 (ADP-glucose pyrophosphorylase large subunit 1) promoter from watermelon (Citrullus vulgaris S.) has proved to exhibit fruit-specific expression patterns in tomato (Lycopersicon esculentum L.). A plant expression vector harboring sweet-taste protein, Brazzein, directed by AGPL1 promoter, was constructed and transferred into tomato plants through Agrobacterium-mediated transform methods. Histochemical staining assay, PCR screening, Southern blotting analysis and RT-PCR analysis showed that Brazzein gene was successfully integrated into the genome of transgenic tomato plants with stable expression. Sweet-taste fruits were produced under control of fruit-specific AGPL1 promoter, whereas other parameters of fruit quality were largely unchanged.

[Recent advances in strawberry transgenic research].

Strawberry (Fragaria ananassa Duch.) is one of most important fruit crops cultivated widely in world. Genetic transformation has launched a new era in strawberry breeding and germplasm creativity. It offers a direct method of creating varieties that selectively targets gene or a few heterologous traits for introduction into the strawberry plant. Great advances have been made in strawberry genetic transformation in the past years. This paper reviews the recent progress in genetic transformation of strawberry on promoting resistance to viruses and fungi, insects, herbicides, stress and quality improvement. Problems and the prospects for application of genetic transformation in strawberry were discussed.

[Photosynthetic acclimation to elevated CO2 in strawberry leaves grown at different levels of nitrogen nutrition].

Photosynthetic characteristics of strawberry (Fragaria ananassa Duch cv. 'Toyonoka') leaves grown in either elevated CO(2) (700 microL/L) or ambient CO(2) (390 microL/L), and at three levels of nitrogen nutrition (12 mmol/L, 4 mmol/L, 0.4 mmol/L) were studied. The results showed that for strawberry grown in 12 mmol/L nitrogen, P(n), maximal carboxylation rate (V(c, max)), maximal linear electron flow through photosystem II (J(max)), electron flow to the photosynthetic carbon reduction cycle (J(c)) and q(P) were all significantly higher in plants grown and measured at elevated CO(2) than for plants grown and measured at ambient CO(2) (Table 1 and 2, Fig. 2), which were due to a significant increase in J(c) exceeding any suppression of electron flow to the photorespiratory carbon oxidation cycle (J(o)). This increase in photochemistrical quenching with decreased non-photochemistrical quenching (q(N) or NPQ) at elevated CO(2) alleviated photoinhibition by high light (Table 2, Fig. 3). For plants grown at 4 mmol/L and 0.4 mmol/L nitrogen, P(n), V(c, max), J(c) and q(P) were all significantly lower in plants grown and measured at elevated CO(2) than for plants grown and measured at ambient CO(2) (Table 1 and 2, Fig. 2). Consistent with decreased photochemistrical quenching and increased non-photochemistrical quenching (q(N) or NPQ), for leaves grown at 4 mmol/L and 0.4 mmol/L nitrogen, the photoinhibition was aggravated by elevated CO(2) (Table 2, Fig. 3). Elevated CO(2) suppressed J(o) in leaves of plants grown at 12 mmol/L, 4 mmol/L and 0.4 mmol/L nitrogen (Fig. 2). The results above suggested that deficient nitrogen (4 mmol/L and 0.4 mmol/L nitrogen) and elevated CO(2) result in an acclimatory decrease of photosynthesis in leaves of plant grown in elevated CO(2).

[Carbohydrate metabolism during fruit development of bayberry (Myrica rubra Sieb. et Zucc.)].

The dynamics of dry and fresh weight, the glucose, fructose, sucrose, titratable acid contents, and activities of sucrose-metabolizing and hexose-metabolizing enzymes were examined in developing fruits of bayberry (Myrica rubra Sieb. et Zucc. cvs. 'Wuzi' and 'Biqi'). The results showed the dry and fresh weight of bayberry fruit increased with fruit development and maturation (Fig. 1), with the highest increase rate of dry matters and water occurring during later stage of fruit development (about 10 d before maturation). The change in titratable acid followed a course of "low-high-low" in developing bayberry fruits (Fig. 3). The titratable acid content reached its peak at about 18 d before fruit maturation, and then decreased rapidly. The sugar compositions in fruits of bayberry cv. 'Wuzi' were different from those in fruits of bayberry cv. 'Biqi'. The main sugar accumulated in fruits of bayberry cv. 'Wuzi' was sucrose, accounting for 2/3 of total sugars but the sucrose content in fruits of bayberry cv. 'Biqi' was below 50% of total sugars. The fructose content in fruits of bayberry cv. 'Wuzi' was 4% higher, but that in fruits of bayberry cv. 'Biqi' was 12% lower than glucose content (Fig. 2). The activities of sucrose cleavage enzymes (invertase and cleavage activity of SS) in the fruit of bayberry cv. 'Biqi' increased with fruit development and maturation, but those activities in fruit bayberry cv. 'Wuzi' were almost stable during fruit development with lower levels of enzyme activities in fruit of cv. 'Wuzi' than in cv. 'Biqi' throughout fruit development (Fig. 4 and Fig. 5A). The SPS activity increased during fruit development (Fig. 6), however, the activity peak of synthetic activity of SS occurred at the middle stage of fruit development (Fig. 5B). The FRK activity in fruit of bayberry cv. 'Wuzi' was higher than that of HXK, but the reverse was in fruit of bayberry cv. 'Biqi' (Fig. 7). These results suggested that the 2-3 weeks before fruit maturation was a key phase for the bayberry development and the formation of fruit quality. There was a correlation between water transport and dry matter accumulation. The different sucrose constitutions between two varieties may be attributed to the differences in the activity levels of the sucrose cleavage enzymes while the difference in the ratio of glucose content to fructose content may be caused by the different activity levels of the hexose-metabolizing enzymes.

[Genetic transformation of peach immature cotyledons with its antisenes ACO gene].

Genetic transformation of peach immature cotyledons with its ACO antisense gene was studied by using particle bombardment method through Agrobacterium tumefaciens. Kanr shoots and Kanr plantlet were obtained. The plantet with ACO antisenes gene through Agrobacterium tumefaciens was obtained by micrografting technique and survived for nearly one month. The results of the PCR, PCR-southern, genomes southern hybridization analysis and GUS color reaction of some Kanr materials showed in some degree that the peach ACO antisens gene was integrated into peach genomes.

[Sugar metabolism and its regulation in postharvest ripening kiwifruit].

Kiwifruit (Actinidia deliciosa cv. Bruno) was used to investigate starch and sugar metabolism and the mechanisms of regulation by acetylsalicylic acid (AsA 1.0 mmol/L, pH 3.5), low temperature (0 degrees C) and ethylene (100 microL/L) treatments. There was an increase in amylase activity at the initial stage followed by dramatical decrease in starch content and a rapid increase in hexose content at the rapid stage of fruit ripening and softening, which was associated with an increase in SPS activity, a decrease in acid invertase activity, and the accumulation of sucrose. AsA and low temperature treatments inhibited the amylase activity, slowed down the hydrolysis of starch and the accumulation of hexoses, suppressed the rise of SPS activity and the decline of acid invertase activity in the ripening fruit. The accumulation of sucrose was delayed by AsA and low temperature treatments. However, ethylene application induced amylase activity, accelerated starch hydrolysis, and raised the hexose content. The SPS activity also increased and the sucrose accumulated in the presence of ethylene. It is suggested that the SPS may play a key role in sugar metabolism of postharvest kiwifruit, and it could be activated by hexose and feedback-inhibited by sucrose. AsA, low temperature and ethylene treatments regulate sugar metabolism probably through influencing the SPS activity.

[Sugar transport, metabolism, accumulation and their regulation in fruits].

Photosynthates transported into fruits are mainly in the form of sucrose in most fruit tree species; but sorbitol takes the place of sucrose in woody Rosaceae plants. The transport of sugars across the plasma membrane from apoplastic space into cells is mediated by sugar transporters. The fact that gene expression of sugar transporters is upregulated just before and during sugar accumulation suggests the participation of sugar transporters in sugar accumulation of fruit. The sucrose-metabolizing enzymes participate in four futile cycles that involve sugar transport between cytosol, vacuole, amyloplast and apoplast. The increase in SS (sucrose synthase) and SPS (sucrose phosphate synthase) activities and mRNA levels during maturation parallels the increase in sugar accumulation indicates that the sucrose-metabolizing enzymes have important roles on sugar accumulation in fruits. The prerequisite for rapid accumulation of sugar in fruit is restriction of hexose catabolism and promotion of its synthesis. In woody Rosaceae plants, the fact that sucrose metabolism is also quite active in fruit suggests that sorbitol and sucrose probably play similar roles in fruit development. Sugars as signal molecules regulate the expression of genes involved in sugar transport and metabolism. Sugar transport, metabolism and accumulation are also regulated by natural environmental factors and cultural practices. The increase in sugar content of tomato fruit in acid invertase gene antisense-inhibited plants provides promising prospect of genetic engineering as a potential effective technique in regulation of sugar accumulation in fruits. Thus, the sugar content of fruit is determined by both intrinsic and extrinsic factors. The future research works will be focused on elucidating the mechanism of sugar signal and other intrinsic signals as well as extrinsic signals including nutrients, plant hormones and physical factors on sugar transport, metabolism and accumulation and the interrelationship among them.

[The relationship of fructokinase and sugar accumulation during fruit development in satsuma mandarin].

Sugars accumulation and fructokinase activity during satsuma mandarin fruit development in relation to the effect of extra nitrogenous fertilizer on the activity and expression of fructokinase were studied. The results exhibited that fructokinase activity in the tissues of edible and peel decreased during fruit development, which coincided with the accumulation of sugars, while the contents of sucrose and glucose decreased, and the activity of the enzyme increased in peel tissues of ripened fruit. After fertilizing with extra urea, the ratios of sucrose and fructose decreased in ripe fruit, while that of glucose increased compared to the control. The activity of fructokinase presented on a protein basis increased in treated fruit. Northern analysis confirmed that extra nitrogenous fertilizer enhanced the expression of Cufrk1 at the late stage of fruit development, but had no effect on Cufrk2. The results suggest that the two different genes of citrus FRK may play distinct roles in sink metabolism and Cufrk1-encoded fructokinase protein could be induced by fertilization with extra nitrogen.

[An efficient macro-method of genomic DNA isolation from Actinidia chinensis leaves].

It is a difficult problem to isolate high quality DNA from plants containing a high contents of polyphenolics and polysaccharose, such as Actinidia plant. The protocol described in this paper is a modified CTAB (hexadecyltrimethylammonium bromide) method. High quality genomic DNA can be isolated from Actinidia plant using the improved method. The DNA is good enough for Southern blot and other uses in DNA research. The protocol is also efficient for quick and macro-DNA extraction.

[Effects of elevated CO2 on photoinhibition of strawberry leaves under different nitrogen levels].

By using PAM-2000 portable chlorophyll fluorometer and HCM-1000 photosynthesis measurement system, this paper measured the initial fluorescence (Fo), maximal photochemical efficiency of PSII (Fv/Fm), maximal fluorescence (Fm), amount of inactive PS II reaction centers (Fi-Fo), proportion of Q(B)-non-reducing PS II reaction centers [(Fi-Fo)/(Fp-Fo)], and net photosynthetic rate (Pn) of strawberry leaves under conditions of elevated CO2 (700 microl x L(-1)) and ambient CO2 (390 microl x L(-1)) at three levels of nitrogen application (12, 4 and 0.4 mmol x L(-1)). The results showed that there was a significant joint effect between CO2 and N on the photoinhibition of strawberry leaves. Under elevated CO2 condition, the Pn in treatment 12 mmol N x L(-1) increased by 62.7%, while that in treatments 4 and 0.4 mmol N x L(-1) decreased by 7.4% and 21.3%, respectively. When exposed to high light and subsequently recovered in dark for 4 hours, the strawberry leaves in treatment 12 mmol N x L(-1) showed less changes of Fm and Fv/Fm in elevated CO2 than in ambient CO2, while those in treatments 4 and 0.4 mmol N x L(-1) were in adverse, suggesting that for the strawberry leaves in elevated CO2, nitrogen deficiency could result in an acclimatized decrease of photosynthesis and an increase of photoinhibition.

[Gene and gene engineering of carotenoid biosynthesis].

Carotenoids have a range of diverse biological functions and actions, especially playing an important role in human health with provitamin A activity, anti-cancer activity, enhancing immune ability and so on. Human body can't synthesis carotenoids by itself and must absorb them from outside. However, carotenoid contents in many plant are very low, and many kinds of carotenoid are difficult to produce by chemical ways. With the elucidation of carotenoid biosynthetic pathway and cloning genes of relative enzymes from microorganisms and higher plants, it is possible to regulate carotenoid biosynthesis via genetic engineering. This article reviews gene cloning of carotenoid biosynthetic enzymes in microorganisms and higher plants, and advances in the studies of carotenoid production in heterologous microorganisms and crop plants using gene-manipulated carotenoid biosynthesis.