Donohue Kathleen, Heschel M Shane, Butler Colleen M, Barua Deepak, Sharrock Robert A, Whitelam Garry C, Chiang George C K
Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave., Cambridge, MA 02138, USA.
Department of Plant Sciences and Plant Pathology, Montana State University, PO Box 173150, Bozeman, MT 59717-3150, USA.
New Phytol. 2008;177(2):367-379. doi: 10.1111/j.1469-8137.2007.02281.x. Epub 2007 Nov 17.
Environmental conditions during seed maturation influence germination, but the genetic basis of maternal environmental effects on germination is virtually unknown. Using single and multiple mutants of phytochromes, it is shown here that different phytochromes contributed to germination differently, depending on seed-maturation conditions. Arabidopsis thaliana wild-type seeds that were matured under cool temperatures were intensely dormant compared with seeds matured at warmer temperature, and this dormancy was broken only after warm seed-stratification followed by cold seed-stratification. The warm-cold stratification broke dormancy in fresh seeds but not in dry after-ripened seeds. Functional PHYB and PHYD were necessary to break cool-induced dormancy, which indicates a previously unknown and ecologically important function for PHYD. Disruption of PHYA in combination with PHYD (but not PHYB) restored germination to near wild-type levels, indicating that PHYA contributes to the maintenance of cool-induced dormancy on a phyD background. Effects of seed-maturation temperature were much stronger than effects of seed-maturation photoperiod. PHYB contributed to germination somewhat more strongly in seeds matured under short days, whereas PHYD contributed to germination somewhat more strongly in seeds matured under long days. The variable contributions of different phytochromes to germination as a function of seed-maturation conditions reveal further functional diversification of the phytochromes during the process of germination. This study identifies among the first genes to be associated with maternal environmental effects on germination.
种子成熟期间的环境条件会影响种子萌发，但母体环境对种子萌发影响的遗传基础几乎尚不明确。本文利用光敏色素的单突变体和多突变体表明，不同的光敏色素对种子萌发的作用因种子成熟条件而异。与在较高温度下成熟的拟南芥野生型种子相比，在低温下成熟的种子具有很强的休眠性，且这种休眠只有在经过暖层积处理后再进行冷层积处理才能打破。暖冷层积处理能打破新鲜种子的休眠，但对干燥后熟种子无效。功能性的PHYB和PHYD对于打破低温诱导的休眠是必需的，这表明PHYD具有此前未知且在生态学上很重要的功能。PHYA与PHYD（而非PHYB）同时缺失可使种子萌发恢复到接近野生型水平，这表明在PHYD背景下，PHYA有助于维持低温诱导的休眠。种子成熟温度的影响比种子成熟光周期的影响要强烈得多。在短日照条件下成熟的种子中，PHYB对种子萌发的促进作用稍强，而在长日照条件下成熟的种子中，PHYD对种子萌发的促进作用稍强。不同光敏色素对种子萌发的作用随种子成熟条件而变化，这揭示了光敏色素在种子萌发过程中进一步的功能多样化。本研究首次鉴定出与母体环境对种子萌发影响相关的基因。
