Matrix-assisted laser desorption/ionization-time of flight mass spectrometry imaging (MALDI-TOF MSI) is a powerful technique that can visualize the distribution of chemical compounds in a tissue specimen without using antibodies or staining. In the case of strawberry fruit, while distribution of soluble carbohydrates, organic acids and anthocyanins have been visualized utilizing MALDI-TOF MSI, the methodology has seldom been used to explore the distribution of plant hormones including abscisic acid (ABA). It is well known that ABA plays an important role in fruit maturation and may act as a seed germination inhibitor in strawberry fruit, as reported for watermelon. However, since the concentration of ABA in strawberry fruit is quite low, it has not been detected utilizing MALDI-TOF MSI. To visualize the distribution of ABA in strawberry fruit, we used the Enomoto method, where the sample is pretreated with Girard’s reagent T (GirT). In this study, a thin (100 µm) specimen of a fully matured fruit of ever-bearing type strawberry (‘Suzuakane’), which had been frozen and stored at -80°C, was cut on a cryomicrotome, and then mounted on an indium tin oxide (ITO)-coated glass slide. After several trials to improve on the Enomoto method, we succeeded in finding suitable pretreatment conditions for detecting ABA in strawberry fruit. The specimen, which was sprayed previously with GirT and α-cyano-4-hydroxycinnamic acid (CHCA) as a matrix, revealed that the concentration of ABA was relatively high in the cortex tissue, and at the vascular bundle conjugated with achenes. This finding may lead to a better understanding of the mechanisms of fruit maturation and the inhibition of seed germination in strawberry fruit.
Takumi Fujiki won the ISHS Young Minds Award for the best poster presentation at the X International Strawberry Symposium in China in March 2025.
Takumi Fujiki, Graduate School of Agriculture, Hokkaido University, Kita 9-jo, Nishi 9-chome, Kita-ku, Sapporo 0608589, Japan, e-mail: takumi_496@eis.hokudai.ac.jp
The article is available in Chronica Horticulturae