矮牵牛花朵大小遗传规律及相关基因的表达分析

Inheritance Analysis of Flower Size and Expression of Related Genes in Petunia hybrida

花朵大小是植物进化及物种形成过程中的关键因子,也是决定植物观赏价值的重要性状,研究其遗传规律与调控机制具有重要的科学意义和实用价值。以不同花朵大小的矮牵牛(Petunia hybrida)自交系和原生种为材料,配制大花×中花和大花×小花杂交组合,构建遗传群体,研究其花朵大小的遗传规律。结果表明,大花自交系W与腋花矮牵牛S26(中花)杂交F_(1)群体均为大花,F_(2)群体中大花与中花的分离比接近3:1,BC1回交群体中大花与中花的分离比接近1:1;大花自交系W与中花自交系S杂交F_(1)群体均为大花, F_(2)群体花朵大小出现分离,大花与中花的比例接近2:1;大花自交系W与膨大矮牵牛S6 (小花)杂交F_(1)群体均为中花, F_(2)群体则出现花径从大到小的连续分布。利用主基因+多基因混合模型分析,按照AIC值最小的标准选出W×S26组合的最优模型为1MG-AD, W×S的最优模型为2MG-EAD,由此判定W大花对S26中花由1对主显性基因控制,具加性-显性效应,W大花对S中花则由2对主基因控制,具等加性-显性效应。此外,根据前期大、小花转录组分析结果,选取9个可能调控花朵大小的基因,通过qPCR检测了它们在不同花朵大小的矮牵牛株系花瓣中的表达水平,结果发现细胞分裂素受体基因PhHK以及响应细胞分裂素信号的type-ARRs基因在大花中的表达水平普遍高于中花和小花,表明细胞分裂素信号途径可能是参与调控矮牵牛大花性状的关键因素。

Flower size is a key factor in plant evolution and speciation,and also an important trait that determines plant ornamental value,so it is of great scientific significance and practical value to study the inheritance law and regulatory mechanism of floral size.To clarify the inheritance law of flower size in petunia,the inbred lines and wild species of Petunia hybrida with different flower sizes were used to make cross combinations and construct genetic populations in this study,including large-flowered line×medium-flowered lines(W×S26 and W×S)and large-flowered line×small-flowered line(W×S6).The results showed that all F_(1) generation of W×S26 were large-flowered plants,while the flower size appeared separation in F_(2) population with the ratio between large-and medium-flowered individuals of about 3:1,and the segregation ratio between large-and medium-flowered plants was close to 1:1 in the BC1 backcross population.For the W×S combination,all F_(1) individuals were large-flowered,while the flower size appeared separation in the F_(2) population,with large-to medium-flowered plants close to 2:1.The F_(1) progenies of W×S6 are all medium-flowered plants,while the flower size of the F_(2) generation showed evident variation and continuous distribution.Performing mixed major gene plus polygene inheritance model analysis,the optimal models for W×S26 and W×S combination were 1MG-AD and 2MG-EAD,respectively,according to the standard of minimum AIC value.It is reasonable to conclude that the large flower trait of the inbred line W is controlled by a single dominant gene related to the middle flower trait of S26,with additive dominant effect,whereas the large flower of the inbred line W is controlled by two major genes related to the small flower of the inbred lines with equal additive dominant effect.In addition,nine genes that may regulate flower size of petunia were selected based on the transcriptomic analysis of large and small flowers,and their expression levels were detected in the petals of various strains with different flower sizes by qRT-PCR.The results showed that the expression levels of cytokinin receptor gene PhHK and Type-A RRs in response to cytokinin signal were generally higher in large flowers than in medium and small flowers,suggesting that cytokinin signaling pathway may be a key factor involved in regulating the large flower trait in petunia.