互花米草育性基因Pollen Tube Blocked 1的自然变异及其表达与自交结实的相关性

Natural variation of fertility gene Pollen Tube Blocked 1 and the correlation of its expression with self-fertilization of Spartina alterniflora

互花米草(Spartina alterniflora)作为我国当前主要入侵植物之一,其高纬度地区种群的结实率显著高于低纬度地区种群,推测很可能发生了自交进化.为研究其内在遗传机制,选取8个不同纬度地区的互花米草种群为材料,对影响种子结实的主效基因Pollen Tube Blocked 1(SaPTB1)进行扩增并测序以检测单核苷酸多态性(single nucleotide polymorphism,SNP)位点,再通过实时荧光定量PCR(RT-qPCR)方法检测其表达,并通过套袋实验检测种群的自交结实情况.结果显示:SaPTB1中存在两个SNP位点,其中一个位点的变异导致天冬氨酸和天冬酰胺的替换,形成单倍型1和单倍型2;两种单倍型广泛分布于整个沿海地区,与自交结实率无明显相关性.RT-qPCR定量结果显示,该基因在最高纬度(东营)和最低纬度(雷州)的两个种群中表达水平高于其他种群.对不同种群的自交结实情况分析表明,中国的互花米草具有一定的自交结实能力,尤其在SaPTB1表达水平最高的东营和雷州种群中,其自交结实率也是最高的,说明SaPTB1的表达对互花米草的结实具有重要影响.

Spartina alterniflora is one of the most invasive plant species in China.Previous studies showed that populations in high latitude areas had higher seed setting rates than those in low latitude,leading to speculation of evolution of self-fertility.To study the genetic mechanism,we selected 8 populations of S.alterniflora as materials to clone and sequence SaPTB1,a major gene that affects seed setting,and to identify single nucleotide polymorphism(SNP)sites.Real time quantitative PCR(RT-qPCR)and bagging experiments were used to test the expression level of SaPTB1 and self-fertilization seed setting rate,respectively.The results showed that two SNP sites were found in SaPTB1 and one of them led to an amino acid substitution,aspartic acid to asparagine,forming two haplotypes.The two haplotypes were widely distributed in the entire coastal area of China and had no obvious correlation with seed setting rate of self-fertility.RT-qPCR quantification showed that two populations in highest(DY)and lowest(LZ)latitudes had distinct higher expression levels than others.Moreover,statistically significant results of bagging experiments in self-fertilization seed setting indicated that populations of S.alterniflora in China had the ability of self-fertility especially for the DY and LZ populations.Our study suggests that the expression of SaPTB1 has an important influence on the seed setting rate of S.alterniflora.