Abstract:
In order to investigate the impact of climatic factors on the quality of Siraitia
grosvenorii fruits pollinated in different seasons and the underlying molecular mechanism
involved, the differences in climate factors, quality traits, and gene expression between fruits of
the main cultivar S. grosvenorii “Qingpiguo” pollinated in summer and autumn were statistically
analyzed by monitoring climate factors at different developmental stages, measuring
morphological changes, detecting mogroside metabolism, and analyzing gene expression using
qRT-PCR. The results were as follows: (1) compared to summer-pollinated fruits, the average
temperature and effective accumulated temperature of autumn-pollinated fruits decreased
significantly after 35 d. Additionally, the temperature difference between day and night increased
significantly before 65 d. However, this difference was still less than that of the average
temperature and effective accumulated temperature. The light intensity and air humidity remained
similar. (2) The transverse diameters, longitudinal diameters, and single fruit weights of
autumn-pollinated fruits increased compared to those of summer-pollinated fruits, however, these
differences were not statistically significant. (3) Mogroside V and 11-O-mogroside V in
autumn-pollinated fruits accumulated slowly from 55 d with a delay of about 10 days, moreover,
the content of both compounds in ripe fruits decreased by 40.66 % and 46.07 %, respectively. (4)
The number and extent of up-regulated mogroside V genes were relatively lower, and their
co-expression consistency was poorer. Furthermore, the glucosyltransferase gene SgUGT94-289-3,
responsible for the final step in mogroside V biosynthesis, exhibited down-regulation at all time
points of 55 d. In summary, the shape and size of S. grosvenorii fruits pollinated in different
seasons were not significantly affected by climatic factors; however, the content of mogroside V
was significantly influenced by the temperature, which potentially influences these variations in
mogroside V by regulating both the co-expression consistency and expression level of mogroside
V genes. The results of this study can provide theoretical basis for high-quality cultivation and
genetic breeding of S. grosvenorii.