Data from: Genetic basis of priority effects: insights from nectar yeast

Priority effects, in which the order of species arrival dictates community assembly, can have a major influence on species diversity, but the genetic basis of priority effects remains unknown. Here, we suggest that nitrogen scavenging genes previously considered responsible for starvation avoidance may drive priority effects by causing rapid resource depletion. Using single-molecule sequencing, we de novo assembled the genome of the nectar-colonizing yeast, Metschnikowia reukaufii, across eight scaffolds and complete mitochondrion, with gap-free coverage over gene spaces. We found a high rate of tandem gene duplication in this genome, enriched for nitrogen metabolism and transport. Both high-capacity amino acid importers, GAP1 and PUT4, present as tandem gene arrays, were highly expressed in synthetic nectar and regulated by the availability and quality of amino acids. In experiments with competitive nectar yeast, Candida rancensis, amino acid addition alleviated suppression of C. rancensis by early arrival of M. reukaufii, corroborating that amino acid scavenging may contribute to priority effects. Because niche pre-emption via rapid resource depletion may underlie priority effects in a broad range of microbial, plant and animal communities, nutrient scavenging genes like the ones we considered here may be broadly relevant to understanding priority effects.优先效应（Priority effects）是指物种到达顺序决定群落组装的生态过程，可对物种多样性产生显著影响，但其遗传基础至今仍未明确。本研究提出，此前被认为用于规避氮饥饿的氮清除基因，可能通过快速消耗资源来介导优先效应。本研究利用单分子测序（single-molecule sequencing）技术，对花蜜定植酵母梅奇酵母（Metschnikowia reukaufii）完成了从头基因组组装，获得包含8个骨架序列与完整线粒体基因组的组装结果，基因区域实现无间隙覆盖。研究发现该基因组中存在高频串联基因复制事件，且这些复制事件显著富集于氮代谢与转运相关通路。两种高容量氨基酸转运蛋白基因GAP1与PUT4均以串联基因阵列形式存在，在人工合成花蜜中呈现高表达水平，且其表达受氨基酸的可用性与质量调控。通过与竞争性花蜜酵母假丝酵母（Candida rancensis）开展竞争实验，本研究发现添加氨基酸可缓解梅奇酵母早期定植对假丝酵母的抑制作用，证实氨基酸清除功能确实参与介导优先效应。鉴于通过快速资源消耗实现的生态位抢占可能广泛存在于微生物、植物与动物群落的优先效应过程中，本研究中所关注的这类营养清除基因，或可成为理解跨类群优先效应的通用机制。