<i>LcMYB1</i> Is a Key Determinant of Differential Anthocyanin Accumulation among Genotypes, Tissues, Developmental Phases and ABA and Light Stimuli in <i>Litchi chinensis</i>

<div><p>The red coloration of litchi fruit depends on the accumulation of anthocyanins. The anthocyanins level in litchi fruit varies widely among cultivars, developmental stages and environmental stimuli. Previous studies on various plant species demonstrate that anthocyanin biosynthesis is controlled at the transcriptional level. Here, we describe a litchi R2R3-MYB transcription factor gene, <i>LcMYB1</i>, which demonstrates a similar sequence as other known anthocyanin regulators. The transcription levels of the <i>LcMYB1</i> and anthocyanin biosynthetic genes were investigated in samples with different anthocyanin levels. The expression of <i>LcMYB1</i> was strongly associated with tissue anthocyanin content. <i>LcMYB1</i> transcripts were only detected in anthocyanin-accumulating tissues and were positively correlated with anthocyanin accumulation in the pericarps of 12 genotypes. ABA and sunlight exposure promoted, whereas CPPU and bagging inhibited the expression of <i>LcMYB1</i> and anthocyanin accumulation in the pericarp. <i>Cis-</i>elements associated with light responsiveness and abscisic acid responsiveness were identified in the promoter region of <i>LcMYB1</i>. Among the 6 structural genes tested, only <i>LcUFGT</i> was highly correlated with <i>LcMYB1</i>. These results suggest that <i>LcMYB1</i> controls anthocyanin biosynthesis in litchi and <i>LcUFGT</i> might be the structural gene that is targeted and regulated by <i>LcMYB1</i>. Furthermore, the overexpression of <i>LcMYB1</i> induced anthocyanin accumulation in all tissues in tobacco, confirming the function of <i>LcMYB1</i> in the regulation of anthocyanin biosynthesis. The upregulation of <i>NtAn1b</i> in response to <i>LcMYB1</i> overexpression seems to be essential for anthocyanin accumulation in the leaf and pedicel. In the reproductive tissues of transgenic tobacco, however, increased anthocyanin accumulation is independent of tobacco's endogenous MYB and bHLH transcriptional factors, but associated with the upregulation of specific structural genes.</p>