Chin Ho Lin

Photosynthetic responses of grafted bitter melon seedlings to flood stress

Abstract Young seedlings of bitter melon ( Momordica charantia L. cv. New Known You #3) grafted onto luffa ( Luffa cylindrica Roem. cv. cylinder #2) rootstocks were investigated for adaptation of photosynthetic activities under flooding conditions. Flooding treatment of grafted bitter melon seedlings reduced leaf photosynthetic rate, stomatal conductance, transpiration, soluble protein, and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) as compared with control seedlings. However, the effects were milder than those on ungrafted bitter melon. Furthermore, leaf internal CO 2 concentration, per cent activation of rubisco, and starch content were similar in control and flooded seedlings, and no significant increase in leaf dark respiration rate was observed. Grafting of flood-intolerant bitter melon seedlings onto the flood-tolerant luffa rootstock improved flood tolerance.

Effect of flood stress on morphology and anaerobic metabolism of Momordica charantia

Abstract Flooding induced several morphological and physiological changes in bitter melon (Momordica charantia L.), a flood-intolerant plant; hypocotyl cross-sectional area and numbers of adventitious roots increased significantly after 4 days of flooding. On the first day of flooding, aerobic respiratory rate of flooded roots dropped to 42% of the control level. Activities of alcohol dehydrogenase (ADH) and endogenous concentrations of ethanol increased gradually, reaching a maximum level on the third day of flooding. Concomitantly, an isozymic form of ADH was shown to be induced. An increase in the apparent Km for the ADH substrate, acetaldehyde, was found to be positively correlated with the decline of endogenous concentrations of ethanol after the 3 day flood stress. A prolonged accumulation of ethanol in flood-stressed roots was shown to lead to death of the seminal root system.

Rapid optimization of electroporation conditions for plant cells, protoplasts, and pollen

The optimization of electroporation conditions for maximal uptake of DNA during direct gene transfer experiments is critical to achieve high levels of gene expression in transformed plant cells. Two stains, trypan blue and fluorescein diacetate, have been applied to optimize electroporation conditions for three plant cell types, using different square wave and exponential wave electroporation devices. The different cell types included protoplasts from tobacco, a stable mixotrophic suspension cell culture from soybean with intact cell walls, and germinating pollen from alfalfa and tobacco. Successful electroporation of each of these cell types was obtained, even in the presence of an intact cell wall when conditions were optimized for the electroporation pulse. The optimal field strength for each of these cells differs, protoplasts having the lowest optimal pulse field strength, followed by suspension cells and finally germinating pollen requiring the strongest electroporation pulse. A rapid procedure is described for optimizing electroporation parameters using different types of cells from different plant sources.

Analysis of upregulated cellular genes in pseudorabies virus infection: use of mRNA differential display

Virus infection usually alters the host cell and shuts off the synthesis of cellular macromolecules. In order to screen the upregulated cellular transcripts during pseudorabies virus (PRV) infection, we employed the mRNA differential display technique. The screen is based on positive selection at the mRNA level for genes expressed in normal cells but increased in corresponding PRV-infected cells. Over 14000 species of mRNA, isolated from mock-infected and PRV-infected Madin-Darby bovine kidney cell at 1 h post infection, were screened, and 40 candidate clones were recovered. Southern blot analysis revealed that 17 out of 40 candidate clones, were enhanced in PRV-infected cells. Partial DNA sequences demonstrated that 17 clones were distinct cellular genes, including those encoding the modulators of signal transduction (saposin, 14-3-3, adenylate kinase, adenylyl cyclase, protein kinase C-alpha), those encoding the components of translation (fau, ribosomal proteins S11, L31, L36), other cellular genes (peptidase, cyclin E, rch1, oligo-C-rich single-stranded nucleic acid binding protein, rap, arginyl-tRNA synthetase), and two unknown genes. Thus, this study identifies successfully the transcriptionally regulated cellular genes which are associated with PRV infection. Furthermore, this study provides support for the use of mRNA differential display as a method to rapidly isolate differentially expressed genes in virus infection.

Cold water treatment promotes ethylene production and dwarfing in tomato seedlings

Abstract Tomato ( Lycopersicon esculentum Mill.) seedlings that were treated with cold water (5 °C) once a day, starting 14 d after sowing, were only 80% as tall as the control (25 °C water) plants after 21 d. The dwarfing effect was most conspicuous on the first internode length. Hypocotyl diameter and shoot fresh and dry weights were not significantly affected. A single cold water treatment induced ethylene production that peaked 60–90 min after treatment and then declined. Shoot segments excised above the first node had the highest rate of ethylene production. A single cold water treatment on day 21 resulted in an ethylene production rate of 19.6 nl h –1 g –1 , compared to 3.4 nl h –1 g –1 for control seedlings (an increase of 5.8 times). Daily cold water treatment of 14-d-old seedlings for 2 weeks was equivalent to pretreatment with 3 mg l –1 of ethephon. Pretreatment of seedlings with 1 nl l –1 1-methylcyclopropane (1-MCP) was sufficient to block the ethylene action induced by the cold water treatment. It is inferred that cold water-induced dwarfism of tomato seedlings is mediated through ethylene action.