Real-time Analysis of Photoassimilate Translocation in Intact Eggplant Fruit using 11CO2 and a Positron-emitting Tracer Imaging System

Abstract

A recently developed positron-emitting tracer imaging system (PETIS) noninvasively produces quantitative realtime images of the movement of various compounds in plants. To clarify the mechanism of the growth and development of the fruit of eggplant (Solanum melongena L.), we fed 11 CO 2 to a leaf and monitored the translocation of 11 C-labeled photoassimilate into the fruit by PETIS. Continuous images of the translocation of [11 C]photoassimilate from the leaf to the fruit and inside the fruit were produced, with a shorter time resolution than reported previously. 11 C signal intensity in the fruit increased gradually, and its distribution was not uniform. The fruits were sliced after PETIS measurement and exposed to the imaging plates of a bio-imaging analyzer system. The resultant images showed the localization of 11 C activity inside the fruit, and indicated that translocation of photoassimilate within the fruit was not uniform. The velocity of photoassimilate translocation in the peduncle and changes in the rate of translocation of photoassimilate in the fruit were estimated by analysis of PETIS data. The velocity of photoassimilate translocation through the peduncle was estimated as 1.17 cm·min −1. About 60 min after the start of 11 CO 2 feeding, the 11 C activity of the fruit began to increase, and by 120 min it had reached about 8% of feeding 11 CO 2 . These results indicate that it took about 60 min for the first [11 C]photoassimilates to reach the fruit. Real time observation of photoassimilate translocation within a fruit has never been reported. PETIS may be a powerful tool for revealing the mechanisms of fruit development and maturity.

Metabolism and Accumulation of Sugars Translocated to Fruit and Their Regulation

“…Fruit can use both pathways depending on the species, organs and the developmental stage. Recently, translocation of assimilate was easily detected in eggplant fruit by using a positron-emission tracer imaging system (Kikuchi et al, 2008). Analysis of various fruits is expected in the future.…”

Plant-PET Scans: In Vivo Mapping of Xylem and Phloem Functioning

“…Voxel: the 3D counterpart of a pixel. may contribute significantly [25,[36][37][38][39][40][41][42][43] (Figure 2). This short-lived isotope can be widely used because of the presence of carbon in many plant molecules.…”

“…In storage organs, including roots and fruits, sectoriality has been observed, with specific leaves supplying assimilates to specific parts of the organ [38,39]. Consecutive PET measurements on these storage organs can map the active zones as well as the distribution of assimilates, which is imperative for us to better understand the growth and development of such important structures [38][39][40]. Carbon transport and its sectoriality can also be studied in stems with PET [42].…”

“…Roots, that are otherwise difficult to investigate, can be imaged with PET [41], and this permitted clear analysis of active root tips [44]. In storage organs, including roots and fruits, sectoriality has been observed, with specific leaves supplying assimilates to specific parts of the organ [38,39]. Consecutive PET measurements on these storage organs can map the active zones as well as the distribution of assimilates, which is imperative for us to better understand the growth and development of such important structures [38][39][40].…”

Physiological Roles of Polyols in Horticultural Crops

“…Zhang et al (2004) provided evidence of the spatial localization of a functional monosaccharide transporter for apoplastic phloem unloading in developing apple fruit. For future studies, noninvasive analysis using a positron-emitting tracer imaging system will be useful for real-time observations of photoassimilate translocation (Kikuchi et al, 2008).…”