在小麦遗传学的这场游戏上，加州大学戴维斯分校的Jorge Dubcovsky实验室赢得了一个大满贯。他们在十几年内第四次发现控制小麦春化的基因。这项成果于8月底发表在《美国科学院学报》（PNAS）上。

小麦从种子萌动以后，其生长点除了要求一定的综合条件外，还必须通过一个以低温为主导因素的影响时期，然后才能抽穗、结实，否则终生不实，这一现象称为小麦的春化（vernalization）；这段低温影响时期称为小麦的春化阶段。

研究发现，新鉴定的VRN-D4基因及另外三个对应的基因对了解春化过程和改良小麦品种很关键。同时，一些小麦品种的春季生长习性可追溯到古代种植在南亚地区的小麦，也就是现在的印度和巴基斯坦地区。

大约8000年前，小麦出现在欧亚之间里海（Caspian Sea）的沿海地区。之后，它迅速在两个大洲上扩散，如今在世界各地广泛种植。科学家将其适应性归功于快速变化的基因组，而大多数小麦都有两组或三组染色体。

在寒冷的气候条件下，春化过程确保了怕冷的开花部位避开了冬天最寒冷的那几个月，正好赶上温暖的春天。这样的“冬小麦”可以在秋天种植，在初夏收获。相比之下，“春小麦”品种就没有春化的要求，可以在春天种植，在秋天收获。这适合那些冬天特别寒冷的地区。

“我们对了解适应性变化很感兴趣，特别是春化，它发生在农业的早期扩张阶段，”文章的第一作者、Dubcovsky实验室的博士生Nestor Kippes谈道。由于春化控制开花时间，故它对植物的繁殖成功很重要，同时也能提高小麦、大麦及其他温带谷物的产量。

尽管全世界每年生产7亿多吨小麦，但迅速增长的世界人口仍要求小麦及其他主要农作物的产量继续提高。而长期的全球气候变化，也让提高农作物产量这项任务更具挑战性。

“我们发现，VRN-D4的调控区域有着与其他VRN-A1共同的突变，它们可用来调控春化反应。这些以前未知的等位基因为育种人员提供了新的工具，来改造更好地适应不同环境的小麦品种，”作者写道。（来源：生物通 薄荷）

Identification of the VERNALIZATION 4 gene reveals the origin of spring growth habit in ancient wheats from South Asia

Abstract  Wheat varieties with a winter growth habit require long exposuresto low temperatures (vernalization) to accelerate flowering. Natural variation in four vernalization genes regulating this requirement has favored wheat adaptation to different environments. The first three genes (VRN1–VRN3) have been cloned and characterized before. Here we show that the fourth gene, VRN-D4, originated by the insertion of a ∼290-kb region from chromosome arm 5AL into the proximal region of chromosome arm 5DS. The inserted 5AL region includes a copy of VRN-A1 that carries distinctive mutations in its coding and regulatory regions. Three lines of evidence confirmed that this gene is VRN-D4: it cosegregated with VRN-D4 in a high-density mapping population; it was expressed earlier than other VRN1 genes in the absence of vernalization; and induced mutations in this gene resulted in delayed flowering. VRN-D4 was found in most accessions of the ancient subspecies Triticum aestivum ssp. sphaerococcum from South Asia. This subspecies showed a significant reduction of genetic diversity and increased genetic differentiation in the centromeric region of chromosome 5D, suggesting that VRN-D4 likely contributed to local adaptation and was favored by positive selection. Three adjacent SNPs in a regulatory region of the VRN-D4 first intron disrupt the binding of GLYCINE-RICH RNA-BINDING PROTEIN 2 (TaGRP2), a known repressor of VRN1 expression. The same SNPs were identified in VRNA1 alleles previously associated with reduced vernalization requirement. These alleles can be used to modulate vernalization requirements and to develop wheat varieties better adapted to different or changing environments.

原文链接：http://www.pnas.org/content/early/2015/08/27/1514883112.full.pdf?sid=4b89129d-a87d-4c46-8d63-7589f6c7e583