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

Abstract

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 (NPQ max ), 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 NPQ max 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 CO 2 , 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 NPQ max due to an increase in xanthophyll pigments coupled with enhanced electron flow through the water-water cycle and CEF-PSI.

Environmental Regulation of Heterosis in the Allopolyploid Arabidopsis suecica

“…Our data are also in line with a previous study that showed that allopolyploid soy bean lines with greater capacity for photoprotection might have specifically expanded their geographical range into areas with more light intense environments (Coate et al, 2013). It is appealing to speculate that the niche expansion in soybean (Glycine max) might have also been facilitated by hybrid vigor that was only realized under altered environmental conditions.…”

“…This could potentially lead to variation in levels of enzymes involved in the biochemical aspects of photosynthesis between allopolyploids and their progenitors or even among allopolyploid siblings or lineages. This might be the reason why studies addressing photosynthetic changes due to allopolyploidy are less frequent in the literature (Coate et al, 2012;Coate et al, 2013).…”

Polyploidy and novelty: Gottlieb's legacy

“…Vyas et al [95] discovered that increased levels of RuBisCO in first-generation synthetic tetraploid Phlox drummondii created an unbalanced complement of photosynthetic components, but still yielded a net photosynthetic gain that increased over subsequent generations as balance between gene products was optimized, pointing again towards the importance of both wholegenome duplication per se in generating novelty immediately, also the role of subsequent evolution in shaping it. The allopolyploid Glycine dolichocarpa exhibits enhanced photoprotection under conditions of excess light through overexpression of genes associated with both xanthophyll production and electron flow [103].…”

Evolution of physiological responses to salt stress in hexaploid wheat

“…For example, Coate et al (6) showed that tolerance to chronic light stress was significantly increased in a newly formed allotetraploid of soybean (Glycine dolichocarpa) compared with its diploid progenitors. Neoallopolyploid tobacco (Nicotiana miersii × Nicotiana attenuata) showed an innovation of defense against herbivores (7).…”