Mung Bean Hypocotyl Sections Research Articles

Isolation and expression of an elongation‐dependent gene of mung bean (Vigna radiata) hypocotyl

A cDNA clone of an auxin up‐regulated gene, ARG8, was isolated from hypocotyl sections of etiolated mung bean [Vigna radiata (L.) Wilczek] seedlings by differential screening. The deduced amino acid sequence suggested that ARG8 may encode a cell wall protein. The steady state mRNA level of ARG8 increased by treatment of hypocotyl sections not only with indole‐3‐acetic acid (IAA) but also with fusicoccin, and the auxin inducibility was inhibited by the addition of 0.3 M mannitol in the incubation medium. This indicated that it was not auxin but elongation that regulated the expression of ARG8. The promoter activity of the 5′‐flanking region of ARG8 was determined by assaying the transient expression of a luciferase fusion gene that was introduced into mung bean hypocotyl sections by the particle bombardment technique. The basal activity of the ARG8 upstream region was about a few tenths of that of a modified cauliflower mosaic virus 35S promoter, and it was increased a few fold by treatment with IAA. The auxin inducibility was completely suppressed by the addition of mannitol. A 5′‐deletion analysis showed that a 53‐bp region in the ARG8 promoter was important for the basal and elongation‐dependent promoter activities.

Isolation of plasma membranes from mung bean hypocotyl sections by two-phase partitioning: suitability of the technique for ageing tissues

Isolation of plasma membranes from mung bean hypocotyl sections by two-phase partitioning: suitability of the technique for ageing tissues

Isolation of plasma membranes from mung bean hypocotyl sections by two‐phase partitioning: suitability of the technique for ageing tissues

This paper discusses the application of a particular two‐phase partitioning system to the isolation of plasma membranes from heterogeneous starting material, differing in physiological age. Plasma membranes were isolated from hypocotyl segments of mung beans (Vigna radiata L. Wilczek) on four successive days in order to examine the variation caused by ageing of the seedling. Additionally, the segments were cut at different positions of the hypocotyl to measure variation caused by position‐related ageing. To assess purity and degree of contamination of the plasma membrane‐enriched preparations, a series of membrane enzyme markers were screened for all isolated fractions. Glucan synthetase II activities were enriched in the plasma membrane fractions, but enrichment and recovery became less pronounced with increasing age. Plasma membrane ATPase activity affected by VO43‐, Ca2+ and K+ was similar in all segments throughout the time‐course of the experiment (4 days). However, control ATPase activity varied with segment origin: the physiologically oldest segments showed only 75% activity compared to the youngest ones. Km and Vmax values indicated a smaller proportion of active enzyme but higher substrate affinity as the age of the segments increased. Contamination by intracellular membranes was minimal and unrelated to tissue age.

Inhibition of activity of the ethylene-forming enzyme by α(p-chlorophenoxy)isobutyric acid

α(p-Chlorophenoxy)isobutyric acid (PCIB) inhibited indole-3-acetic acid (IAA)-induced ethylene production in etiolated mung bean hypocotyl sections. The endogenous level of 1-aminocyclopropane-1-carboxylic acid (ACC) was not significantly affected by PCIB, indicating that PCIB exerted its effect primarily by inhibiting the activity of the ethylene-forming enzyme (EFE). This conclusion was supported by the observations that PCIB inhibited the conversion of exogenously applied ACC to ethylene. The inhibitory effect of PCIB was already evident with 0.05 mM PCIB, and it increased with time after application of the inhibitor. PCIB also significantly inhibited ethylene production in apple fruit tissues, but it only slightly reduced the level of endogenous ACC. Similar to mung bean, EFE activity in apple tissue was significantly inhibited by PCIB. The possibility that PCIB also inhibits auxin-induced ACC synthase activity is discussed.

Ethylene and ethane production in response to salinity stress

Abstract Ethylene and ethane production in mung bean hypocotyl sections were evaluated as possible indicators of stress due to contact with four salts that are common in natural sites. Ethylene production decreased with increasing concentrations of applied NaCl and KCl. When CaCl2 was applied, the ethylene evolution was greater. However, when MgCl2 was applied, ethylene evolution remained high then decreased and at higher salt concentrations again showed an increase. NaCl (up to 0.1 kmol m−1) and KCl (up to 0.5 kmol m−3) caused a concentration‐dependent increase in ethane production. The ethane production with CaCl2 was the lowest among the salts tested and only a minute increase was noticed with the increase of concentration from 0.01 to 1 kmol m−3. Ethane production showed a distinct maximum at 0.2 kmol m−3 MgCl2. The introduction of 0.01 kmol m−3 CaCl2, as well as anaerobic conditions obtained by purging vials with N2, eliminated that high ethane production. Respiratory activity of the mung bean hypocotyl sections in MgCl2 concentrations from 0 to 0.5 kmol m−3 was correlated with ethane but not with ethylene production. The ethane/ethylene ratio showed three patterns for the four salts tested.

High Temperature Sensitivity of Auxin-induced Ethylene Production in Mung Bean Hypocotyl Sections

High Temperature Sensitivity of Auxin-induced Ethylene Production in Mung Bean Hypocotyl Sections

A Possible Regulation of Ethylene Production by the Epidermis in Mung Bean Hypocotyl Sections

A Possible Regulation of Ethylene Production by the Epidermis in Mung Bean Hypocotyl Sections

Phytochrome and potassium uptake by mung bean hypocotyl sections

Uptake of potassium (K) and (86)rubidiumlabelled potassium ((86)Rb) by sub-hypocotyl hook sections of Phaseolus aureus L. was inhibited by red light. The effect was reversible with far red light. Using short exposures of high irradiance the effect on (86)Rb-labelled K uptake was observed after 5 min. The response showed no specificity for a particular anion. Uptake of (86)Rb-labelled K by sections cut immediately below the cotyledons was enhanced by red light after 10 min incubation and was also far red reversible. These results are interpreted as a rapid phytochrome-induced change in membrane properties resulting in modified K uptake.

Regulation of sterol biosynthesis in etiolated mung bean hypocotyl sections

The incorporation of radioactivity into sterols by transmethylation of methionine-[ 14C-methyl] was studied in mung bean hypocotyl sections. Young hypocotyl sections (1 cm) synthesized 4 times more radioactive sterols than older sections (5 cm). The transmethylation reactions may be rate limiting in older tissues. Wounding has only a quantitative effect on sterol biosynthesis, as seen by incorporation experiments with MVA-[2- 14C]. Naphthalene acetic acid (NAA) stimulates sterol biosynthesis in both wounded surfaces and intact tissues of mung bean hypocotyl sections.

Hormonal control of sterol biosynthesis in Phaseolus aureus

Naphthalene acetic acid increased the sterol content of mung bean hypocotyl sections mainly in the zone of elongation growth. The increased sterol synthesis can be explained by a stimulated conversion rate of cycloartenol into sterols. During the 20-hr incubation period the stigmasterol: sitosterol ratio increased considerably.

Effect of isopropyl-N-(3-chlorophenyl) carbamate on the production of ethylene by mungbean hypocotyl sections

Effect of isopropyl-N-(3-chlorophenyl) carbamate on the production of ethylene by mungbean hypocotyl sections

A proteinaceous inhibitor of ethylene biosynthesis by etiolated mungbean hypocotyl sections

A protein which reversibly inhibits auxin-induced ethylene synthesis has been isolated and purified from hypocotyls of etiolated mungbean (Phaseolus aureus Roxb.) seedlings. The molecular weight of the inhibitor was estimated to be 112 000 by gel filtration and polyacrylamide gel-electrophoresis. When treated with sodium dodecylsulfate, the inhibitor gave on polyacrylamide gel-electrophoresis a single band corresponding to a molecular weight of 56 000, indicating that it consisted of two subunits with identical molecular weight. The inhibitor does not degrade nor bind indole-3-acetic acid, and has no peroxidase activity.

Studies on soluble RNA binding indoleacetic acid in etiolated mung bean hypocotyl sections

Studies on soluble RNA binding indoleacetic acid in etiolated mung bean hypocotyl sections