Ribonucleic acid (RNA) quantification is an essential technique in biology. There has been remarkable progress in RNA quantification techniques over the recent years; however, the specificity of these techniques to quantify a very small amount of RNA is doubtful because of factors which can inhibit precise quantification. To develop a technique that leads to the most sensitive RNA quantification, these problems must be overcome. In this article, we first review the factors that inhibit precise quantification of RNA: the quality of RNA, secondary structure of RNA, efficiency of the enzyme reaction, annealing conditions, limitations of the experimental protocol and equipment, and detection sensitivity of the equipment. Next, we discuss the possible methods which contribute to these factors: RNA quality control focused on target RNA degradation, isothermal amplification, techniques for avoiding amplification errors, RNase H-dependent PCR, targeting using a fluorescent-labeled probe, targeting using a padlock probe, bridged/locked nucleic acid (BNA/LNA) and peptide nucleic acid (PNA), and the clustered regularly interspaced short palindromic repeat (CRISPR) system. One of the goals for the development of an ultrasensitive RNA quantification technique is the absolute quantification of RNA. Here, we discuss the techniques used for this type of RNA quantification.
Citrus ‘Harumi’ is a mandarin-type cultivar and shows a wide range of fruit size, which affects fruit quality such as sugar and acid contents. In citrus, fruit size also affects the degree of physiological disorder which become a big problem during storage. Thus, making fruit with equal and appropriate size is very important. Fruit thinning is one of the most important techniques to adjust fruit size by controlling the fruit number. Basically, fruit thinning has been conducted using a criterion based on leaf and fruit ratio (L/F) or fruit number per canopy volume. In this review, several thinning criteria for ‘Harumi’ and other citrus varieties are compared, and the pros and cons are discussed. In some citrus varieties, storage is necessary to adjust shipping time. During the storage, some physiological disorders occurred in peel, flesh and whole fruit. The occurrence of physiological disorders was influenced by citrus variety, fruit size and environmental conditions during storage. In ‘Harumi’ which is classified to easy-peeling variety, small fruit showed serious weight loss and peel wrinkle, while rind puffing and dehydration of flesh were big problems in large fruit during storage. Polyethylene (PE) bag wrapping has been used to decrease the fruit weight loss and to prevent the occurrence of some physiological disorders in tight-skin citrus varieties. However, the influences of PE wrapping on easy-peeling citrus is unclear. In this study, the researches on storage conditions, feature, and cause of physiological disorders during storage are also reviewed, and the effects of PE wrapping are discussed to improve storage condition in ‘Harumi’.
The Fusarium fujikuroi species complex (FFSC) is a cosmopolitan fungal lineage with production of a broad spectrum of secondary metabolites including mycotoxins, pigments and plant hormones. The FFSC includes many important plant pathogens. Fusarium fujikuroi, a member of the FFSC, causes rice bakane disease and has been recognized as the exclusive gibberellin (GA) producer for a long time. However, other species such as Fusarium proliferatum, Fusarium sacchari and Fusarium konzum in the FFSC were also identified to produce GA in recent 20 years. GA biosynthesis is conferred by a gene cluster including 7 adjacent genes (GA gene cluster). Expression of the GA genes is activated under limited nitrogen conditions. GA low- or non-production in most FFSC species was revealed to attribute to a partial deletion of the GA gene cluster, malfunction or low expression of the GA genes although the cause has not been fully elucidated. It has been reported that transcriptional factors, signaling components, global regulators and histone modification are involved in regulation of the GA gene expression.
Fumonisin is a worldwide mycotoxin that has devastating implications for human and animal health and food security. The principal source of fumonisin contamination is the members of the Fusarium fujikuroi species complex (FFSC). A cluster (FUM gene cluster) of 16 co-expressed genes (FUM) responsible for fumonisin biosynthesis has been identified and characterized in Fusarium verticillioides. The FUM gene cluster has been detected from other members of the FFSC. In this review, the fumonisin production ability and the status of the FUM gene cluster in 3 clades (African, American, and Asian) of the FFSC have been presented. The comprehensive studies revealed that intraspecific variation is caused by several types of mutations in the FUM gene cluster. In addition, we summarized the regulatory genes involving fumonisin biosynthesis. A comparative study of fumonisin production ability and regulatory mechanism of fumonisin biosynthesis provides valuable insight for control of the mycotoxin contamination.