Julián Cuevas

Pollen from different olive tree cultivars contains varying amounts of the major allergen Ole e 1.

Background: Commercial olive pollen from uncertain cultivar origin is the common material used for clinical and biological studies. We aimed to assess the putative heterogeneity of olive cultivars with regard to the presence of the major pollen allergen Ole e 1 and to determine whether these differences have clinical relevance. Methods: The Ole e 1 content of several cultivars was determined by immunoblotting and ultrastructural immunocytochemistry and compared to that of a commercially available olive pollen extract designed for diagnosis. Reverse transcription-polymerase chain reaction analysis of Ole e 1 transcripts was also performed. Crude protein extracts were used to carry out skin prick tests (SPTs) on 30 allergic patients in order to evaluate the clinical importance of such differences. Results: Ole e 1 was present in all cultivars, although significant quantitative differences were detected. Ole e 1 transcripts positively correlated with the amount of the allergen. Significant variations in the average reactivity of allergic patients to SPTs were observed depending on the cultivar considered. Conclusions: The presence of the Ole e 1 allergen in all the cultivars suggests that this allergen may play an essential biological role. The expression of the allergen is controlled at the transcriptional level. The significant differences in the Ole e 1 content are likely responsible for the different average reactivity exhibited by patients to the cultivars studied, although the role of other allergens cannot be excluded. Our results suggest that the use of the commercial pollen mixtures currently available may lead to mistakes in allergy diagnosis and to limited success in immunotherapy. Therefore, further standardization is strongly recommended.

Standardization of the fluorochromatic reaction test to assess pollen viability

The fluorochromatic reaction that viable pollen grains exhibit when exposed to fluorescein diacetate (FDA) is an easy, quick and accurate tool for assessing pollen viability in many plants. Despite its widespread use, the method as initially proposed by Heslop-Harrison and Heslop-Harrison lacks specificity in some respects that are essential for comparing simultaneously the viability of different pollen sources. We have determined the time needed for the fluorochromatic reaction to take place and fade, and the lifetime and most effective concentration of the FDA working solution. Our results show that consistent records of pollen viability in samples of olive (bicellular pollen grains) and cherimoya (tricellular pollen grains) can be obtained within minutes, but that measurement must be completed in the first hour after pollen exposure to FDA. The lifespan of the FDA working solution is 1 h, whereas concentrations between 1.5×10−5 M and 1.8×10−3 M are equally valid. Pollen grains of both species responded similarly, although some differences were observed in the persistence of fluorochromasia.

Loquat fruit sink strength and growth pattern

Abstract Loquat fruit growth measured by increases of equatorial diameter adjusts to a logistic curve. By means of sequential measurements of tagged fruits of cultivar ‘Algerie’, curves were obtained that fit significantly to a single sigmoid model in unthinned as well as in heavily thinned trees. Equations defining growth pattern of fruits from thinned and from unthinned trees showed different slopes that reflect greater growth rates under thinning. On the contrary, small and large fruits within the same tree showed minor variations in growth rates, and fruit size at harvest was largely due to fruit size at initial fruit set. Differences in size among fruitlets of the same tree at the time of hand fruit thinning never reversed and led to different commercial categories related with initial size; that allows us to recommend fruit thinning on a size basis. A strong significant correlation was also found at harvest between fresh fruit weight and equatorial diameter. Size and number of seeds were the major determinants of final fruit size in loquat whereas number of leaves and leaf area index of the bearing shoots showed a weak correlation with final size of fruits.

The sex-determining gene CitACS4 is a pleiotropic regulator of flower and fruit development in watermelon (Citrullus lanatus)

In the species of the Cucurbitaceae family, the occurrence of separate male and female flowers in the same plant (monoecy) is controlled by an ethylene biosynthesis ACS gene, which specifically suppresses the development of stamen in the female flower. In watermelon, a mutation of loss of function in CitACS4 promotes the conversion of female into hermaphrodite flowers, and of monoecious into andromonoecious plants. We have studied whether the ethylene produced by CitACS4 enzyme could also be involved in other ethylene-regulated traits, including pistillate flowering transition and the number of female flowers per plant, the development of floral organs other than stamens, as well as fruit and seed set, and fruit development. A linkage analysis approach was performed in three independent F2 populations segregating for the two alleles of the gene (M, monoecious; m, andromonoecious), and the different traits under study. The CitACS4m allele not only cosegregated with andromonoecy, but also with earlier pistillate transition, an increased number of pistillate flowers per plant, and a slower growth and maturation of petals and carpels, which delayed anthesis time in hermaphrodite flowers. The m allele was also found to be linked to a reduced fruit set, which was not caused by a deficiency in pollination or fertilization. The gene also affected the longitudinal and transverse growth rates of the ovary and fruit, which means that fruits from andromonoecious plants (mm) were rounder than those from monoecious (MM) ones. Taken together, these data indicate that the locus defined by the ethylene biosynthesis and sex-determining gene CitACS4 acts as a pleiotropic regulator of the complete development of the pistillate flower and the earlier development of the fruit.