Varieties of
Citrus
are commercially important fruits that are cultivated worldwide and are valued for being highly nutritious and having an appealing flavor. Lignification of citrus fruit juice sacs is a serious physiological disorder that occurs during postharvest storage, for which the underlying transcriptional regulatory mechanisms remain unclear. In this study, we identified and isolated a candidate MYB transcription factor, CsMYB85, that is involved in the regulation of lignin biosynthesis in
Citrus sinensis
, which has homologs in
Arabidopsis
and other plants. We found that during juice sac lignification,
CsMYB85
expression levels increase significantly, and therefore, suspected that this gene may control lignin biosynthesis during the lignification process. Our results indicated that CsMYB85 binds the
CsMYB330
promoter, regulates its expression, and interacts with CsMYB308 in transgenic yeast and tobacco. A transient expression assay indicated that
Cs4CL1
expression levels and lignin content significantly increased in fruit juice sacs overexpressing CsMYB85.
At4CL1
expression levels and lignin content were also significantly increased in
Arabidopsis
overexpressing CsMYB85. We accordingly present convincing evidence for the participation of the CsMYB85 transcription factor in fruit juice sac lignification, and thereby provide new insights into the transcriptional regulation of this process in citrus fruits.
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