Abstract
Plants have evolved several mechanisms for sensing increased irradiance, involving signal perception by photoreceptors (cryptochromes), and subsequent biochemical (reactive oxygen species, ROS) and metabolic clues to transmit the signals. This results in the increased expression of heat‐shock response genes and of the transcription factor LONG HYPOCOTYL 5 (HY5, mediated by the cryptochrome photoreceptor 1, CRY1). Here, we show the existence of another response pathway in Arabidopsis. This pathway evokes the SPX1‐mediated expression activation of the transcription factor PHR1 and leads to the expression of several galactolipid biosynthesis genes. Gene expression analysis of accessions Col‐0, Ga‐0, and Ts‐1, showed activated expression of the SPX1/PHR1‐mediated gene expression activation pathway acting on galactolipids biosynthesis genes in both Ga‐0 and Col‐0, but not in Ts‐1. The activation of the SPX1/PHR1‐mediated response pathway can be associated with lower photosynthesis efficiency in Ts‐1, compared to Col‐0 and Ga‐0. Besides the accession‐associated activation of the SPX1/PHR1‐mediated response pathway, comparing gene expression in the accessions showed stronger activation of several heat responsive genes in Ga‐0, and the opposite in Ts‐1, when compared to Col‐0, in line with the differences in their efficiency of photosynthesis. We conclude that natural variation in activation of both heat responsive genes and of galactolipids biosynthesis genes contribute to the variation in photosynthesis efficiency in response to irradiance increase.
Highlights
The light‐use efficiency of photosynthesis is the result of the molecular, structural, and physiological state of the plant (Eberhard, Finazzi, & Wollman, 2008; Foyer, Neukermans, Queval, Noctor, & Harbinson, 2012; Zhu, Long, & Ort, 2008), which depends on many environmental factors
Arabidopsis accessions Col‐0, Ga‐0 and Ts‐1 were grown for 24 days under 100 μmol m−2 s−1 growth irradiance, and from the day onwards exposed to an irradiance of 550 μmol m−2 s−1, which is saturating for photosynthesis in these low‐ light grown plants
We investigated in Quantitative real‐time reverse transcriptase PCR (qRT‐PCR) two genes involved in alternative splicing SERINE-ARGININE RICH RNA BINDING PROTEIN 45a (SR45a) (At1 g07350) and SR30 (At1 g09140); two transcription factors GOLDEN2-LIKE 2 (GLK2) (At5 g44190) and DEHYDRATION RESPONSIVE ELEMENT BINDING 2A (DREB2A) (At5 g05410), three heat‐shock genes HSFA2 (At2 g26150), HOP3 (At4 g12400), and CPN60BETA2 (At3 g13470); and two genes involved in lipid‐remodeling SPX1 (At5 g20150) and GDPD1 (At3 g02040)
Summary
The light‐use efficiency of photosynthesis is the result of the molecular, structural, and physiological state of the plant (Eberhard, Finazzi, & Wollman, 2008; Foyer, Neukermans, Queval, Noctor, & Harbinson, 2012; Zhu, Long, & Ort, 2008), which depends on many environmental factors. Beyond light‐limitation, light‐use efficiency decreases with increasing irradiances, resulting in the overall phenomenon of. A consequence of increased irradiance is an increase in the rate of damaging side reactions of photosynthesis that occur as a result of the reactive nature of many intermediates formed. These reactive intermediates come from redox signals mediated via changes in the degree of thioredoxin and plastoquinone reduction and increased formation of reactive oxygen species (ROS) (Vass, 2012). The regulatory responses of photosynthesis, which are more active during stress (for example qE‐type nonphotochemical quenching or down‐regulation of electron transport at the level of the cytochrome b6/f complex) appear to reduce the formation of ROS, especially under high growth irradiances (Scheibe, Backhausen, Emmerlich, & Holtgrefe, 2005; Suzuki, Koussevitzky, Mittler, & Miller, 2012). Different species and genotypes display different capacities to acclimate their photosynthetic apparatus to an irradiance increase so it is reasonable to infer that this is at least partly genetically determined (van Rooijen, Aarts, & Harbinson, 2015; van Rooijen et al, 2017)
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