Reproduction et Développement des Plantes, Université Lyon, Lyon, France.
PLoS One. 2010 Feb 18;5(2):e9288. doi: 10.1371/journal.pone.0009288.
Roses have been cultivated for centuries and a number of varieties have been selected based on flower traits such as petal form, color, and number. Wild-type roses have five petals (simple flowers), whereas high numbers of petals (double flowers) are typical attributes of most of the cultivated roses. Here, we investigated the molecular mechanisms that could have been selected to control petal number in roses.
METHODOLOGY/PRINCIPAL FINDINGS: We have analyzed the expression of several candidate genes known to be involved in floral organ identity determination in roses from similar genetic backgrounds but exhibiting contrasting petal numbers per flower. We show that the rose ortholog of AGAMOUS (RhAG) is differentially expressed in double flowers as compared to simple flowers. In situ hybridization experiments confirm the differential expression of RhAG and demonstrate that in the double-flower roses, the expression domain of RhAG is restricted toward the center of the flower. Conversely, in simple-flower roses, RhAG expression domain is wider. We further show that the border of RhAG expression domain is labile, which allows the selection of rose flowers with increased petal number. Double-flower roses were selected independently in the two major regions for domestication, China and the peri-Mediterranean areas. Comparison of RhAG expression in the wild-type ancestors of cultivated roses and their descendants both in the European and Chinese lineages corroborates the correlation between the degree of restriction of RhAG expression domain and the number of petals. Our data suggests that a restriction of RhAG expression domain is the basis for selection of double flowers in both the Chinese and peri-Mediterranean centers of domestication.
CONCLUSIONS/SIGNIFICANCE: We demonstrate that a shift in RhAG expression domain boundary occurred in rose hybrids, causing double-flower phenotype. This molecular event was selected independently during rose domestication in Europe/Middle East and in China.
玫瑰已经被培育了几个世纪，并且根据花瓣形状、颜色和数量等花朵特征，已经选育出了许多品种。野生型玫瑰有五瓣花瓣（单瓣花），而多数栽培玫瑰的典型特征是花瓣数量多（重瓣花）。在这里，我们研究了可能被选择来控制玫瑰花瓣数量的分子机制。
方法/主要发现：我们分析了几个候选基因在遗传背景相似但每朵花花瓣数量不同的玫瑰中的表达情况。我们表明，与单瓣花相比，玫瑰同源物 AGAMOUS（RhAG）在重瓣花中差异表达。原位杂交实验证实了 RhAG 的差异表达，并表明在重瓣玫瑰中，RhAG 的表达域局限在花的中心。相反，在单瓣玫瑰中，RhAG 的表达域较宽。我们进一步表明，RhAG 表达域的边界是不稳定的，这允许选择具有更多花瓣数的玫瑰花。重瓣玫瑰在两个主要的驯化地区，中国和地中海周边地区，都是独立选择的。对栽培玫瑰的野生型祖先及其后代的 RhAG 表达的比较，无论是在欧洲系还是中国系，都证实了 RhAG 表达域的限制程度与花瓣数量之间的相关性。我们的数据表明，RhAG 表达域边界的限制是欧洲/中东和中国驯化中心选择重瓣花的基础。
结论/意义：我们证明了 RhAG 表达域边界的转移发生在玫瑰杂种中，导致了重瓣花表型。这一分子事件在欧洲/中东和中国的玫瑰驯化过程中是独立选择的。
