Comparative analysis of anatomy, gene expression of Vaccinium corymbosum cyclins and cyclin dependent kinases during the flower bud and fruit ontogeny

Abstract

Cell-cycle system controls flower and fruit growth, size and mass precisely, accompanied by cumulative cell proliferation and cell expansion. Vaccinium corymbosum shows significant variation in berry size, but its underlying anatomical and molecular mechanisms are poorly known. In this study, single fruit mass and cell layers of Southern highbush blueberry cultivars 'O'Neal' and 'Bluerain' were analyzed, and 12 cell-cycle related genes were isolated and detected its expression tendency. The results showed that blueberry flower buds had a lower contribution to mature fruit mass, and fruit growth exhibited a double-sigmoid pattern. Ovary wall (or pericarp) was the vital component for final fruit size, and approximately 70% cell layers of pericarp were produced before anthesis. Cell division in the blueberry fruit was arrested at pre- and post-anthesis. The sequences of Vccyclins and VcCDKs were relatively conserved, and its expression tendency followed flower bud and fruit developmental pattern, while VcCycA2L, VcCycB2L, VcCycD3;1L, VcCycT1;4L, VcCDKB2;2, VcCDKC1L and VcCDKE1 might be directly involved in cell proliferation and cell expansion. However, the difference of expression pattern between two cultivars was not quite significant, indicated that isolated Vccyclins and VcCDKs were not the key factors for blueberry fruit size. Collectively, this study expands our understanding of the complex cell division and cell expansion mechanisms, and cell-cycle regulatory mechanisms were involved in V. corymbosum flower and fruit during ontogeny.