Pollen sterility was induced by heat stress applied about 10 days before flowering in the snap bean Phaseolus vulgaris L. Cytohistological changes in the tapetum during early development of the anther were studied to identify the tissues most sensitive to high temperature stress. The first distinct structural abnormalities were detected in the distribution pattern of the rough endoplasmic reticulum (RER) in the tapetum at the early microspore stage under high temperature conditions. Stacks of RER were frequently observed in the tapetum under optimal conditions, but rarely occurred under high temperature conditions. Various patterns of endoplasmic reticulum (ER) arrangement -linear, wavy, looped or circular -were observed in the tapetum. Two types of circular ER were observed at the microspore stage under high temperature conditions, RER with ribosomes on the surface and smooth endoplasmic reticulum (SER) lacking ribosomes. The tapetum underwent degenerative changes under high temperature conditions earlier than under optimal conditions. The structural abnormalities of the microspore were associated with tapetal degeneration. We concluded that high air temperature affected the ER structure and blocked its function in the tapetum, and then induced earlier than usual degeneration of tapetum. Pollen sterility is associated with tapetal degeneration. Materials and methodsEighty snap bean plants (Phaseolus vulgaris L. cv. Kentucky Wonder) were grown 25 cm apart in four rows, each 1 m wide × 5 m long, in a net house from 18 April at JIRCAS Okinawa Subtropical Station in 1997. About 50 flower buds of different sizes were collected randomly from the plants on 28 May (optimum conditions). The maximum temperature that day was 28.6°C, the minimum 24.4°C and the average 26.2°C. Average air temperature in May was 25.8°C.

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To clarify the cis-trans isomeric effect on the ultrafast DNA photo-cross-linking reaction of 3-cyanovinylcarbazole nucleoside ((CNV)K) in the DNA duplex, which gives a single photodimer on the reversed-phase HPLC chromatogram, the kinetics of the cis-trans photoisomerization of (CNV)K in double-stranded DNA was evaluated. Since the photoisomerization rate constant for cis to trans isomerization in double-stranded DNA was significantly larger than that for trans to cis isomerization, and the thermodynamic stability of the trans isomer was higher than that of the cis isomer, it was strongly suggested that the trans isomer of (CNV)K is a reactive species of the photo-cross-linking reaction. (1)H-(1)H NOESY analysis of the photoadduct consisting of (CNV)K and T also supported the trans-mediated photo-cross-linking reaction of (CNV)K. By using this ultrafast photo-cross-linking reaction for the molecular beacon-based SNPs typing, four individual Japanese rice strains were clearly distinguishable with simple photoirradiation and fluorescence imaging using double-stranded target DNAs.

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