Supplemental light triggers vesicular trafficking in ripening
berry accumulating anthocyanins
The transportation of anthocyanins into vacuoles is usually trafficked
intra-cellularly by different classes of transporter proteins, such as
MATEs, ABCs, and GSTs (Petrussa et al., 2013). The transporters involved
in fruit anthocyanin transport in relation to light quality response
have not been studied. However, our results demonstrated that a set of
genes, including Stx , Bos1, Gos1, Ykt6, Sec20, Sec 22, andSyp7 were highly up-regulated in response to red light treatment.
These genes belonged to the SNARE-domain protein family, which includes
the common syntaxin-like (Stx, Syp ) genes. Interestingly, the
unigenes annotated as Stx -like (1,4) type along with an ABC
transporter were up-regulated in response to red light treatment and
reacted in the opposite manner to that of blue light treatment. Hence,
SNARE domain transporters are candidates to be involved in vesicular
trafficking of anthocyanins or trans-membrane transport from endoplasmic
reticulum (ER) to golgi and endosomes. It also indicates the potential
role of syntaxin genes differentially responding to light-induced
anthocyanin transport mechanisms. These different types of SNAREs,
barring the ER localized Syp and Sec are usually localized
in endosomes and in trans-golgi network (Kim et al., 2012). Our results
may indicate a new route for anthocyanin sequestration and
transportation in fruit tissues. The proposed vesicular trafficking
model of anthocyanins in fruits might be also co-regulated by otherGST s and ABC transporters in addition to the SNARE-domain
type proteins before depositing as anthocyanic vacuolar inclusions (AVI)
in the vacuole (Zhao, 2015). This mechanism could also relate to the
plant tissues that accumulate higher anthocyanin levels under high
intensity light and needs to be investigated further.