中美科學(xué)家近日研究發(fā)現(xiàn),，雜交植物比其親本生長更大更好的原因在于,，它們負責(zé)光合作用和淀粉代謝的基因在白天要更為活躍。這一發(fā)現(xiàn)在農(nóng)業(yè)生產(chǎn)中將具有重要的意義,。相關(guān)論文11月23日在線發(fā)表于《自然》（Nature）雜志上,。
科學(xué)家早已知道，諸如雜交玉米等雜交植物比它們的親本更為健壯,，產(chǎn)量更高,，種子更大。在多倍體植物中也具有類似的現(xiàn)象,，超過70%的開花植物都是天然的多倍體,。然而，科學(xué)家一直未能理解其中的分子機制,。
在最新的研究中,，中國農(nóng)業(yè)大學(xué)的Jeffrey Chen和合作者利用擬南芥研究發(fā)現(xiàn)，在雜交植物和多倍體植物中,，與光合作用和淀粉代謝有關(guān)的基因的表達得到了增加,，在白天的時候,，表達量是其親本的好幾倍,。雜交植物和多倍體植物表現(xiàn)出更多的光合作用,、葉綠素和淀粉積聚，所有這些導(dǎo)致植株更加高大,。
在進一步的研究中,，研究人員在雜交植物和多倍體植物中發(fā)現(xiàn)了生理時鐘調(diào)節(jié)子和生長勢（growth vigor）之間的直接聯(lián)系。生理時鐘控制著植物和動物的生長,、代謝和適切性,。研究人員發(fā)現(xiàn)，在白天的時候,，雜交植物和多倍體植物中的一些調(diào)節(jié)子——轉(zhuǎn)錄抑制子被更多地抑制，導(dǎo)致光合作用和淀粉積聚增加,。
Chen說：“在此次發(fā)現(xiàn)之前,，沒人真正知道雜交和多倍性怎樣增加生長勢，這肯定不是這種現(xiàn)象背后的唯一機制,，但它是一個巨大的進步,。”
他表示，利用這一發(fā)現(xiàn)，他們現(xiàn)在可以開發(fā)基因組和生物技術(shù)工具,，以發(fā)現(xiàn)和培育更好的雜交和多倍體植物,。他說：“我們可以考慮在親本中篩選這些基因，并選擇一些來培育最好的雜交種,。這可以通過傳統(tǒng)的培養(yǎng)技術(shù)來實現(xiàn),，并將在提高燃料作物和糧食作物產(chǎn)量方面產(chǎn)生巨大影響。”（生物谷Bioon.com）
生物谷推薦原始出處：
Nature,，doi:10.1038/nature07523,，Zhongfu Ni，Z. Jeffrey Chen
Altered circadian rhythms regulate growth vigour in hybrids and allopolyploids
Zhongfu Ni1,6,7, Eun-Deok Kim1,6, Misook Ha1,2,3, Erika Lackey1, Jianxin Liu1, Yirong Zhang1,7, Qixin Sun5 & Z. Jeffrey Chen1,2,3,4
1 Section of Molecular Cell and Developmental Biology,
2 Institute for Cellular and Molecular Biology,
3 Center for Computational Biology and Bioinformatics, and,
4 Section of Integrative Biology, The University of Texas at Austin, One University Station, A-4800, Austin, Texas 78712, USA
5 Department of Plant Genetics and Breeding, China Agricultural University, Yuanmingyuan Xilu No. 2, Beijing, 100094, China
6 These authors contributed equally to this work.
7 Present address: Department of Plant Genetics and Breeding, China Agricultural University, Yuanmingyuan Xilu No. 2, Beijing, 100094, China.
Segregating hybrids and stable allopolyploids display morphological vigour1, 2, 3, and Arabidopsis allotetraploids are larger than the parents Arabidopsis thaliana and Arabidopsis arenosa 1, 4—the mechanisms for this are unknown. Circadian clocks mediate metabolic pathways and increase fitness in animals and plants5, 6, 7, 8. Here we report that epigenetic modifications of the circadian clock genes CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY)9, 10, 11 and their reciprocal regulators TIMING OF CAB EXPRESSION 1 (TOC1) and GIGANTEA (GI)10, 12, 13 mediate expression changes in downstream genes and pathways. During the day, epigenetic repression of CCA1 and LHY induced the expression of TOC1, GI and downstream genes containing evening elements14 in chlorophyll and starch metabolic pathways in allotetraploids and F1 hybrids, which produced more chlorophyll and starch than the parents in the same environment. Mutations in cca1 and cca1 lhy and the daily repression of cca1 by RNA interference (RNAi) in TOC1::cca1(RNAi) transgenic plants increased the expression of downstream genes and increased chlorophyll and starch content, whereas constitutively expressing CCA1 or ectopically expressing TOC1::CCA1 had the opposite effect. The causal effects of CCA1 on output traits suggest that hybrids and allopolyploids gain advantages from the control of circadian-mediated physiological and metabolic pathways, leading to growth vigour and increased biomass.
