Data from: Transgressive physiological and transcriptomic responses to light stress in allopolyploid Glycine dolichocarpa (Leguminosae)

Allopolyploidy is often associated with increased photosynthetic capacity as well as enhanced stress tolerance. Excess light is a ubiquitous plant stress associated with photosynthetic light harvesting. We show that under chronic excess light, the capacity for non-photochemical quenching (NPQmax), a photoprotective mechanism, was higher in a recently formed natural allotetraploid (Glycine dolichocarpa, designated ‘T2’) than in its diploid progenitors (G. tomentella, ‘D3’; and G. syndetika, ‘D4’). This enhancement in NPQmax was due to an increase in energy-dependent quenching (qE) relative to D3, combined with an increase in zeaxanthin-dependent quenching (qZ) relative to D4. To explore the genetic basis for this phenotype, we profiled D3, D4 and T2 leaf transcriptomes and found that T2 overexpressed genes of the water–water cycle relative to both diploid progenitors, as well as genes involved in cyclic electron flow around photosystem I (CEF-PSI) and the xanthophyll cycle, relative to D4. Xanthophyll pigments have critical roles in NPQ, and the water–water cycle and CEF-PSI are non-photosynthetic electron transport pathways believed to facilitate NPQ formation. In the absence of CO2, T2 also exhibited greater quantum yield of photosystem II than either diploid, indicating a greater capacity for non-photosynthetic electron transport. We postulate that, relative to its diploid progenitors, T2 is able to achieve higher NPQmax due to an increase in xanthophyll pigments coupled with enhanced electron flow through the water–water cycle and CEF-PSI.

异源多倍性（allopolyploidy）通常与光合能力提升以及抗逆性增强相关。光过剩是一类广泛存在的、与光合光捕获过程相关的植物胁迫。本研究发现，在长期光过剩条件下，新近形成的天然异源四倍体（*Glycine dolichocarpa*，命名为‘T2’）的最大非光化学淬灭（NPQmax）能力——一种光保护机制——高于其二倍体祖先种（*G. tomentella*，‘D3’；以及*G. syndetika*，‘D4’）。该NPQmax的提升，相较于D3源于能量依赖型淬灭（qE）的增强，同时相较于D4则得益于玉米黄质依赖型淬灭（qZ）的提升。为探究该表型的遗传基础，我们对D3、D4和T2的叶片转录组进行了分析，发现T2相较于两个二倍体祖先种均高表达了水-水循环相关基因，同时相较于D4还高表达了光系统I循环电子流（CEF-PSI）以及叶黄素循环相关的基因。叶黄素类色素在非光化学淬灭中发挥关键作用，而水-水循环与CEF-PSI被认为是可促进非光化学淬灭形成的非光合电子传递途径。在无CO₂条件下，T2的光系统II量子产额也高于任一二倍体祖先种，这表明其非光合电子传递能力更强。我们推测，相较于其二倍体祖先种，T2之所以能够实现更高的NPQmax，是因为其叶黄素类色素含量提升，同时通过水-水循环和CEF-PSI的电子流得到增强。