岩桐屬植物之葉脈呈色及花萼瓣化機制

岩桐屬(Sinningia)植物中大岩桐[Sinningia speciosa (Lodd.) Hiern]為重要室內盆花，大岩桐的花色花型多樣，白脈亦具有觀賞價值，為探討葉脈呈色機制及重瓣與白脈的遺傳模式，本研究以重瓣品種絲織品(Brocade)，與其他具特殊性狀之原生種與單株為材料，量測大岩桐白脈之葉片光合作用與白脈成因之構造解剖，釐清大岩桐重瓣與白脈遺傳模式和其他岩桐屬植物花萼瓣化與雄蕊瓣化之遺傳模式，並選育同時具有重瓣與白脈性狀之大岩桐，最後為了探討其B類群基因GLO和花萼瓣化的關聯性，分離並檢測GLO在各輪器官之表現分析。為了釐清葉脈呈色機制，以塑膠包埋切片法觀察大岩桐品系‘SS’ × ‘Brocade Red/White Bicolour’ 之F2 子代中綠脈和白脈的解剖構造，結果顯示綠脈之表皮組織與柵狀組織間緊密相接無氣隙，而白脈之塑膠切片結果為表皮組織與柵狀組織間有許多明顯孔隙。大岩桐品種SS之白脈區域與綠色葉身區域之光合作用速率、氣孔導度、細胞間二氧化碳濃度與蒸散作用速率皆無顯著差異。顯示白脈區域與綠色葉肉區域無光合作用差異，白脈並不會使葉片之光合作用下降。大岩桐重瓣與白脈遺傳試驗中，以重瓣綠脈大岩桐‘Brocade Red/White Bicolour’與單瓣白脈大岩桐品種SS雜交，子代花型分離比例符合1重瓣：1白脈之比例，在此品系第一代中挑選花型為半重辦，葉脈為白脈之單株進行自交，F2子代有綠脈性狀出現，子代性狀比例符合9白脈/重瓣：3白脈/單瓣：3綠脈/重瓣：1綠脈/單瓣之比例，顯示花型與葉脈顏色為獨立遺傳，並無聯鎖關係。在此F2子代中選拔出同時具有白脈與重瓣之大岩桐子代，F2子代之完全重瓣花型具有多一輪雄蕊的瓣化器官重複伴隨雌蕊完全花瓣化，同個品系中亦出現兩側對稱和輻射對稱兩種花朵對稱性狀。為了釐清岩桐屬植物花萼瓣化的遺傳模式，以單瓣原生種S. eumorpha與花萼正常種‘Moonlight’雜交後，後代花萼與雌蕊皆正常；以正常花萼之‘Moonlight’與花萼瓣化‘UN1128’雜交後，後代分離比符合1單瓣：1花萼瓣化之比例。顯示花萼瓣化性狀由一對基因(H/h)所控制，異型合子(Hh)顯性時為花萼瓣化，此基因型之植株雄蕊仍然正常具有稔性但是雌蕊扭曲畸形，因此無法作為母本自交與雜交；同型合子隱性(hh)時表現型為單瓣。一般的迷你岩桐的雄蕊正常且具有花粉，突變種中具有雄蕊瓣化的性狀，五枚雄蕊會完全瓣化但瓣化程度不一，外觀上形成兩輪花冠筒之重瓣花。為了釐清雄蕊瓣化的遺傳模式，將正常雄蕊之迷你岩桐自交，子代全數皆為單瓣，正常雄蕊與雄蕊瓣化品種雜交，第一代之分離比符合4雄蕊瓣化：12單瓣之分離比例，顯示迷你岩桐雄蕊瓣化為隱性上位性遺傳。雄蕊瓣化植株無法產生花粉，但此瓣化性狀不影響雌蕊功能，雌蕊並無畸形或扭曲。花朵成長階段外觀與表皮細胞形態的觀察顯示單瓣岩桐S. cardinalis之花萼為綠色齧齒型，且在花冠筒延伸時花萼已停止延長；花萼瓣化品種Party Dress之花萼為深紅色螯合型，其花萼會隨花冠筒延伸時繼續延伸，形成似兩層花冠筒貌，器官構造拆解顯示花萼瓣化之花萼顏色與內側斑點分布與花瓣極為相像。以SEM觀察單瓣岩桐S. cardinalis與花萼瓣化品種Party Dress完全展開之花朵背腹側之花萼與花瓣，S. cardinalis之背側花萼具有氣孔，花萼瓣化品種Party Dress則無氣孔分布，而細胞形狀亦與花瓣較為相似，呈現橢圓形突起。萃取單瓣岩桐S. cardinalis與花萼瓣化‘Party Dress’全花苞之RNA並以反轉錄聚合酶連鎖反應(RT-PCR)與GLO引子成功分離出兩基因。基因樹(phylogenetic tree)支持分離之基因類群屬於GLO類群。RT-PCR結果顯示在單瓣S. cardinalis中GLO僅侷限表現在第二、三輪器官；然而在花萼瓣化品種Party Dress中GLO異位表現至第一、四輪，即花萼、花瓣、雄蕊和雌蕊皆有GLO表現，推測花萼瓣化和此基因之異位表達有相關性。

關鍵字

氣隙型；光合作用速率；花萼瓣化；雄蕊瓣化；異位表達

並列摘要

Gloxinia [Sinningia speciosa (Lodd.) Hiern] is an important indoor flowering plant. Double- flowered cultivar Brocade, Sinningia species and other hybrid with special traits were included in this study. The objectives were to 1) determine the mechanism and net photosynthesis rate of leaf vein 2) understand flower type, leaf vein coloration, petaloid stamen and petaloid calyx inheritance in selfed and crossed progeny 3) isolate the B-class gene GLO and analyze GLO expression in the four floral whorls. The net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration, and transpiration rate did not differ between the white and green areas of white-veined ‘SS’ leaves. In the green leaf vein areas, the chlorenchyma cells tightly connected to the adaxial epidermal cells. However, intercellular spaces were observed between the adaxial epidermal cells and chlorenchyma cells in the white vein areas. The F2 progenies derived from white-veined ‘SS’ × ‘Brocade Red/White Bicolour’ segregated into a ratio of 9:3:1 of white vein/double flower:white vein/single flower:green vein/ double flower:green vein/single flower. The observed ratio supports that two independent loci control the two traits of vein color and flower form. New gloxinia progeny with homozygous white veins and double flowers were successfully developed from some of the F2 population. Selfing normal calyx Sinningia spp. resulted in all normal calyx progeny. Crossing petaloid calyx and normal calyx parents resulted in a 1 petaloid calyx : 1 normal calyx ratio. Petaloid calyx was proposed as controlled by a single allele (H, h). A single dominant gene expressed in HH or Hh state resulted in petaloid calyxed phenotype and the hh genotype showed normal calyx. Petaloid calyx is linked with deformed pistil. Selfing normal stamen Sinningia spp. resulted in all normal stamen progeny. Crossing petaloid stamen and normal stamen parents resulted in a 4 petaloid stamen : 12 normal stamen ratio. Petaloid stamen was recessive epistasis and proposed as controlled by two alleles (D, d) and (M, m). Genotype expressed in Ddmm resulted in petaloid stamen phenotype and the dd__ genotype showed normal stamen. We examined the morphology and developmental genetics of two different species of Sinningia, one of which, S. cardinalis, has normal sepals while the other, ‘Party Dress’, has two whorls of petal-like organs. Scanning electron microscopy of cell surface morphologies of first and second whorl organs in the double-corolla species ‘Party Dress’ revealed conical epidermal cells on the adaxial surfaces of both first and second whorl petaloid organs, strongly suggesting a homeotic conversion in the former. Phylogenetic analysis of Sinningia species shows clear divergence of Sinningia from outgroup genera Liliaceae and Poaceae, and demonstrates extremely low sequence divergence among Sinningia species. Reverse transcriptase polymerase chain reaction analysis of homologs of the B-function genes GLOBOSA(GLO) indicated ectopic expression of GLO paralogs in the first and fourth whorl of ‘Party Dress’. In the standard sepal-petal species S. cardinalis, ectopic expression of GLO homologs was not observed.