Chromosomal Organization and Sequence Diversity of Genes Encoding Lachrymatory Factor Synthase in Allium cepa L.

Lachrymatory factor synthase (LFS) catalyzes the formation of lachrymatory factor, one of the most distinctive traits of bulb onion (Allium cepa L.). Therefore, we used LFS as a model for a functional gene in a huge genome, and we examined the chromosomal organization of LFS in A. cepa by multiple approaches. The first-level analysis completed the chromosomal assignment of LFS gene to chromosome 5 of A. cepa via the use of a complete set of A. fistulosum–shallot (A. cepa L. Aggregatum group) monosomic addition lines. Subsequent use of an F2 mapping population from the interspecific cross A. cepa × A. roylei confirmed the assignment of an LFS locus to this chromosome. Sequence comparison of two BAC clones bearing LFS genes, LFS amplicons from diverse germplasm, and expressed sequences from a doubled haploid line revealed variation consistent with duplicated LFS genes. Furthermore, the BAC-FISH study using the two BAC clones as a probe showed that LFS genes are localized in the proximal region of the long arm of the chromosome. These results suggested that LFS in A. cepa is transcribed from at least two loci and that they are localized on chromosome 5

Impact of electrostatic atomized water particles (EAWPs) treatment on chlorophyll degradation and delay ripening in Thai banana (Musa paradisiaca, cv. ‘Namwa’ banana) during storage

Electrostatic atomized water particles (EAWPs) treatment was applied to investigate its effect on chlorophyll (Chl) degradation and delaying of ripening in ‘Namwa’ banana. Banana fruits were pretreated with EAWPs generated from a device (Panasonic F-GMK01) for 0 (control), 0.5, 1.0, 1.5, and 3.0 h in a closed 50 L container, and then kept in perfolated polypropylene plastic bags and stored at ambient temperature (25±2 °C) under dark condition. The results showed that 1.0 h-EAWPs treatment best retained peel greenness with a significantly higher hue angle and lower L* value than other treatments on day 6. Also, the 1.0 h-EAWPs treatment maintained the total Chl content, firmness, total soluble solids (TSS) and delayed the ripening index (RI) of fruit accompanied with a delayed climacteric rise of ethylene and respiration rate compared to control. It was found that the 1.0 h-EAWP treatment induced accumulations of nitric oxide (NO) in peel tissues and suppressed the activities of Chl degrading enzymes (chlorophyllase, Mg-dechelatase, Chl-degrading peroxidase, and pheophytinase) in the peel. Furthermore, Chl derivatives levels (chlorophyllide a, pheophobide a, 132-hydroxychlorophyll a, and pheophytin a) were higher in fruits treated with EAWPs than the control fruits. The results suggest that EAWPs technology could be an alternative approach to delay the Chl degradation and ripening in ‘Namwa’ banana

A Dual-Color Tyr-FISH Method for Visualizing Genes/Markers on Plant Chromosomes to Create Integrated Genetic and Cytogenetic Maps

In situ imaging of molecular markers on a physical chromosome is an indispensable tool for refining genetic maps and validation genome assembly at the chromosomal level. Despite the tremendous progress in genome sequencing, the plant genome assembly at the chromosome level remains a challenge. Recently developed optical and Hi-C mapping are aimed at assistance in genome assembly. For high confidence in the genome assembly at chromosome level, more independent approaches are required. The present study is aimed at refining an ultrasensitive Tyr-FISH technique and developing a reliable and simple method of in situ mapping of a short unique DNA sequences on plant chromosomes. We have carefully analyzed the critical steps of the Tyr-FISH to find out the reasons behind the flaws of this technique. The accurate visualization of markers/genes appeared to be significantly dependent on the means of chromosome slide preparation, probe design and labeling, and high stringency washing. Appropriate adjustment of these steps allowed us to detect a short DNA sequence of 1.6 Kb with a frequency of 51.6%. Based on our results, we developed a more reliable and simple protocol for dual-color Tyr-FISH visualization of unique short DNA sequences on plant chromosomes. This new protocol can allow for more accurate determination of the physical distance between markers and can be applied for faster integration of genetic and cytogenetic maps