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论文 |
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| 论文题目: |
Acidic alpha-galactosidase is the most abundant nectarin in floral nectar of common tobacco (Nicotiana tabacum)
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| 论文题目英文: |
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| 作者: |
Zha, Hong-Guang; Flowers, V. Lynn; Yang, Min; Chen, Ling-Yang; Sun, Hang
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| 论文出处: |
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| 年: |
2012
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| 卷: |
109 |
| 期: |
4 |
| 页: |
735-745 |
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| 发表期刊: |
ANNALS OF BOTANY |
| 第一作者所在部门: |
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| 收录类别: |
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| 影响因子: |
2.755
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| 摘要: |
To date, most floral nectarins (nectar proteins) are reported to function in nectar defence, particularly for insect-pollinated outcrossing species. We compared nectarin composition and abundance in selfing common tobacco (Nicotiana tobaccum) with outcrossing ornamental tobacco plants to elucidate the functional difference of nectarins in different reproductive systems. Common tobacco (CT) nectarins were separated by SDS-PAGE and the N terminus of the most abundant nectarin was sequenced via Edman degradation. The full-length nectarin gene was amplified and cloned from genomic DNA and mRNA with hiTail-PCR and RACE (rapid amplification of cDNA ends), and expression patterns were then investigated in different tissues using semi-quantitative reverse transcriptase PCR. Additionally, high-performance liquid chromatography and enzymatic analyses of nectar sugar composition, and other biochemical traits and functions of the novel nectarin were studied. The most abundant nectarin in CT nectar is an acidic -galactosidase, here designated NT-Gal. This compound has a molecular mass of 40 013 Da and a theoretical pI of 533. NT-Gal has a conserved -Gal characteristic signature, encodes a mature protein of 364 amino acids and is expressed in different organs. Compared with 27 other melliferous plant species from different families, CT floral nectar demonstrated the highest -Gal activity, which is inhibited by d-galactose. Raffinose family oligosaccharides were not detected in CT nectar, indicating that NT-Gal does not function in post-secretory hydrolysis. Moreover, tobacco plant fruits did not develop intact skin with galactose inhibition of NT-Gal activity in nectar, suggesting that NT-Gal induces cell-wall surface restructuring during the initial stages of fruit development. -Gal was the most abundant nectarin in selfing CT plants, but was not detected in the nectar of strictly outcrossing sister tobacco species. No function was demonstrated in antimicrobial defence. Therefore, floral nectarins in selfing species maintain their functional significance in reproductive organ development. |
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