以替換式遺傳定位法與關聯式遺傳定位法分析位於se2.1數量性狀基因座附近控制番茄雄蕊長度的遺傳因子

Abstract

柱頭突出程度是決定番茄交配行為的重要因子， se2.1 是位在番茄第二對染色體上控制柱頭突出的數量性狀基因座，其中包含數個與柱頭突出相關的基因，分別控制花柱長度、雄蕊長度及雄蕊管柱的開裂。為了解柱頭凸出的遺傳基礎，本研究使用關聯式遺傳定位法及替換式遺傳定位法針對 se2.1 進行高解析度遺傳定位分析。在關聯式遺傳定位法中使用100個 Solanum lycopersicum var. cerasiforme 選系與99個 S. pimpinellifolium 選系組成的族群進行分析。族群結構分析利用63個分散在基因體中的CAPS標記，藉由貝式統計方法將定位族群分群，用來校正因為族群結構可能產生的偽相關。利用29個CAPS標記觀察兩個物種中連鎖失衡的範圍，由於 S. lycopersicum var. cerasiforme 內有高度連鎖失衡，不適合進行高解析度遺傳定位，因此僅使用 S. pimpinellifolium 族群進行關聯式分析。在關聯式遺傳定位分析中將S. pimpinellifolium 族群分為兩個次族群進行校正，結果顯示在 Style2.1 影響花柱長度的主要遺傳變異有兩個，包括基因轉譯的起始位置及距離起始位置上游4kb外啟動子上450bp 核酸片段缺失處附近。此外，在 Stamen2.2 及 Stamen2.3 所在的染色體區間內，分子標記TAP109顯示與雄蕊長度的變異有統計上顯著的相關。在替換式遺傳定位法中則使用7個在se2.1內不同位置發生重組的滲入系，將外表型結果與親本比較，鑑別出候選基因 Stamen2.1 ，並發現可能存在新的控制雄蕊長度基因 Stamen2.4 。

The degree of stigma exserted above the stamen is a key determinant of mating behavior in tomato. Se2.1 was previously identified as a quantitative trait locus controlling stigma exsertion and is a gene complex affecting style length, stamen length, and anther dehiscence. In the current study, genetic components of se2.1 were further investigated using association mapping and substitution mapping. For association mapping, one hundred Solanum lycopersicum var.cerasiforme accessions and ninety nine S. pimpinellifolium accessions from TGRC were used. Sixty three randomly chosen CAPS markers from the whole tomato genome were used to estimate population structure and defined two sub-populations for the S. pimpinellifolium accessions analyzed. Twenty nine CAPS markers within a 214.78kb genomic contig which contains Style2.1, Stamen2.2, and Stamen2.3 were genotyped to estimate the range of linkage decay in S. lycopersicum var cerasiforme and S. pimpinellifolium populations, respectively. Only the S. pimpinellifolium population showed very short linkage decay and was suitable for high-resolution genetic mapping. The result of association mapping delineated the genetic variations of Style2.1 attributed to phenotypic variations of style length at two sites: one close to the start codon and the other close to the 450bp indel located at 4kb upstream of the start codon. In addition, a statistically significant association between marker TAP109 and stamen length was detected within the genomic region containing Stamen2.2 and Stamen2.3. For substitution mapping, nearly isogenic lines delimiting genes responsible for stamen length in the previous study were evaluated again. In additional to Stamen2.1, existence of additional gene controlling stamen length was suggested.