Calamondin fruit

The capability of Citrus to translocate limonoids from the fruit tissues to the seeds was demonstrated by administering 1 x 10 cpm of methyl- "deacetylnomilinate to the stem end of detached calamondin fruits. After 16 hrs of incubation, 7,500 cpm of activity were translocated to the seeds, and over 90% of the total activity in the seed extract was recovered as the original substrate (8). These results show that limonoids present in citrus seeds are translocated through the fruit tissue. 

At this time, we are improving the purification of all the enzymes involved in the biosynthesis of the mono-, sesqui- and diterpene hydrocarbons present in the essential oils of calamondin fruits and pine needles. Antibodies against the purified enzymes will be further used to localize the enzymes at the cell level by immuno-cytochemistry. 

Sonnen et al. (jl) observed the effect of root temperatures on the fruit color of two citrus cultivars. When comparisons were made with satsumas at 14°C and 30°C and with calamondins at 12°C and 25°C, there were higher amounts of carotenoids and better color in the peel from fruit grown at the lower root temperatures. 

Recently brassinolide was found to retard the abscission of leaf explants of Calamondin (6). Thus, the present experiments were also included to observe the effects of brassinolide on the fruit set of Morita navel oranges (Citrus sinensis), a cultivar derived from Washington navel. 

Explants of Calamondin clearly showed a marked retardation of leaf and fruit abortion (6). Repeated application of brassinolide to intact plants of Calamondin failed to prevent either leaf or fruit abortion (private communication from Dr. Iwahori of Kagoshima University). This suggests that brassinosteroids hardly move into plant abscission zones. Thus, it would be necessary for practical use to find tissues to which brassinosteroids are easily translocated. In contrast it would be almost impossible to use brassinosteroids on young cereal ears to prevent fruit abortion, because they are covered with leaf sheaths. 

The young fruits of calamondin were collected on plants growing in the greenhouse of University Bordeaux I. The maritime pine needles were harvested during their growing period (June-3uly) at the Station d Amelioration des Arbres Forestiers INRA, Pierroton -Cestas, France. 

The PEG precipitate (30- 0%) obtained from the 100,000 g supernatant of the epicarp of immature fruits of calamondin was submitted to chromatography on a column of DEAE-Sephacel and developed with a linear gradient of NaCl (0.1-0.2M). As shown in fig. 1, the limonene and selinene cyclase activities were resolved. The electrophoresis of the fractions involved in mono- and sesquiterpene biosynthesis showed the purification obtained after the DEAE-Sephacel column. Incubations of small gel pieces with [ H]-GPP and [ H]-FPP led to the localization of the cyclases involved in both limonene and selinene synthesis and indicated that the two cyclases are well separated on the gel. In order to improve the purification of these cyclases, the active fractions eluted from the DEAE-Sephacel column were submitted to affinity chromatography using Sepharose APP. This procedure contributed to a 90-fold and 70-fold purification for limonene and selinene cyclases respectively. An isoelectric point of 5A 0.2 was found for limonene-cyclase whereas 3-selinene-cy-clase presented a value of 6 0.2. After gel permeation with Sephadex G 200, the same molecular weight of 67 3 kD was attributed to the two cyclases. In addition, prenyltransferases obtained from a DEAE-Sephacel column developed with a step gradient (0.1, 0.2, 0.3 M NaCl) were also isolated on the same affinity column. These prenyltransferases were 160 fold purified. Their molecular weight was about 70 kD and they exhibited an isoelectric point of 3.2. 

---