The Role of Pigments and Cryptochrome 1 in the Adaptation of Solanum lycopersicum Photosynthetic Apparatus to High-Intensity Blue Light

Abstract

The effects of high-intensity blue light (HIBL, 500/1000 µmol m^-2s^-1, 450 nm) on Solanum lycopersicum mutants with high pigment (hp) and low pigment (lp) levels and cryptochrome 1 (cry1) deficiency on photosynthesis, chlorophylls, phenols, anthocyanins, nonenzymatic antioxidant activity, carotenoid composition, and the expression of light-dependent genes were investigated. The plants, grown under white light for 42 days, were exposed to HIBL for 72 h. The hp mutant quickly adapted to 500 µmol m^-2s^-1 HIBL, exhibiting enhanced photosynthesis, increased anthocyanin and carotenoids (beta-carotene, zeaxanthin), and increased expression of key genes involved in pigment biosynthesis (PSY1, PAL1, CHS, ANS) and PSII proteins along with an increase in nonenzymatic antioxidant activity. At 1000 µmol m^-2s^-1 HIBL, the lp mutant showed the highest photosynthetic activity, enhanced expression of genes associated with PSII external proteins (psbO, psbP, psbQ), and increased in neoxanthin content. This mutant demonstrated greater resistance at the higher HIBL, demonstrating increased stomatal conductance and photosynthesis rate. The cry1 mutant exhibited the highest non-photochemical quenching (NPQ) but had the lowest pigment contents and decreased photosynthetic rate and PSII activity, highlighting the critical role of CRY1 in adaptation to HIBL. The hp and lp mutants use distinct adaptation strategies, which are significantly hindered by the cry1 mutation. The pigment content appears to be crucial for adaptation at moderate HIBL doses, while CRY1 content and stomatal activity become more critical at higher doses.

Keywords: Solanum lycopersicum; blue light; cryptochrome 1; high irradiance; photomorphogenetic mutants; photosynthetic apparatus; pigments.

Figure 1

Spectra of the light sources used in the experiments.

Figure 2

Impact of blue high irradiance exposure on fluorescence parameters: effective quantum PSII yield Y(II) (A), nonphotochemical quenching (NPQ) (C), Y(NO) (B) and Y(NPQ) (D) are PSII quantum yields of nonregulated and regulated nonphotochemical energy dissipation, respectively. Here. Y(NO) + Y(NPQ) + Y(II) = 1. The plants were grown under white fluorescence lamps for 42 days and then exposed to high blue light (I = 500 and 1000 μmol m⁻²s⁻¹) for 72 h. The means ± SD are shown. Different letters within indicate significant differences (p ≤ 0.05) according to ANOVA on ranks followed by Duncan’s method within one particular variant of light and time, n = 6. WT = wild type; cry1 = cryptochrome 1; hp = LA3005 high pigment mutant; lp = LA3617 low pigment mutant.

Figure 3

Changes in the PSII maximum quantum yield (F_v/F_m) of the WT and mutant plants to high intensity blue light. The plants were grown under white fluorescent light for 42 days and then exposed to high blue light (I = 500 or 1000 μmol m⁻²s⁻¹) for 72 h. The means ± SD are shown. Different letters indicate significant differences (p ≤ 0.05) according to ANOVA on ranks followed by Duncan’s method within one particular variant of light and time, n = 6. WT = wild type; cry1 = cryptochrome 1; hp = LA3005 high pigment mutant; lp = LA3617 low pigment mutant.

Figure 4

Changes in the Trolox equivalent antioxidant capacity (TEAC, µM Trolox g⁻¹ FM) after the plants were exposed to high intensity blue light. The plants were grown under white lamps for 42 days and then exposed to high blue light (I = 500 or 1000 μmol (photons) m⁻²s⁻¹) for 24, 48, and 72 h. The means ± SD are shown. Different letters within indicate significant differences (p ≤ 0.05) according to ANOVA on ranks followed by Duncan’s method within one particular variant of light and time, n = 3. WT = wild type; cry1 = cryptochrome 1; hp = LA3005 high pigment mutant; lp = LA3617 low pigment mutant.

Figure 5

Transcript levels of protochlorophyllide oxidoreductase A (PORA), phytoene synthase (PSY1), phenylalanine ammonia-lyase (PAL1), chalcone synthase (CHS), anthocyanin synthase (ANS), elongated hypocotyl 5 (HY5), ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL), early light-induced protein (Elip) (A) and D1 protein of PSII (psbA), D2 protein of PSII (psbD), CP47 (psbB) and CP43 (psbC) proteins involved in the core antenna complex for light harvesting in PSII, the manganese-stabilizing protein essential for the stability of the water-splitting complex in PSII (psbO), proteins that optimize and regulate the oxygen-evolving complex of PSII (psbP and psbQ), and the chlorophyll a/b-binding protein of the light-harvesting complex in PSII (CAB1) (B). The plants were grown under white fluorescent light for 42 days and then exposed to high blue light (I = 500 or 1000 μmol m⁻²s⁻¹) for 24 or 72 h. The means ± SDs are shown. Different letters within indicate significant differences (p ≤ 0.05) according to ANOVA on ranks followed by Duncan’s method within one particular variant of light and time, n = 3. WT = wild type; cry1 = cryptochrome 1; hp = LA3005 high pigment mutant; lp = LA3617 low pigment mutant. The colors indicate the deviation from the mean expression level for each gene, represented by bars. A red color signifies an increase in expression more than twice the average. A white color denotes no significant change from the average. A blue color represents a decrease in expression more than twice the average.

Figure 5

Transcript levels of protochlorophyllide oxidoreductase A (PORA), phytoene synthase (PSY1), phenylalanine ammonia-lyase (PAL1), chalcone synthase (CHS), anthocyanin synthase (ANS), elongated hypocotyl 5 (HY5), ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL), early light-induced protein (Elip) (A) and D1 protein of PSII (psbA), D2 protein of PSII (psbD), CP47 (psbB) and CP43 (psbC) proteins involved in the core antenna complex for light harvesting in PSII, the manganese-stabilizing protein essential for the stability of the water-splitting complex in PSII (psbO), proteins that optimize and regulate the oxygen-evolving complex of PSII (psbP and psbQ), and the chlorophyll a/b-binding protein of the light-harvesting complex in PSII (CAB1) (B). The plants were grown under white fluorescent light for 42 days and then exposed to high blue light (I = 500 or 1000 μmol m⁻²s⁻¹) for 24 or 72 h. The means ± SDs are shown. Different letters within indicate significant differences (p ≤ 0.05) according to ANOVA on ranks followed by Duncan’s method within one particular variant of light and time, n = 3. WT = wild type; cry1 = cryptochrome 1; hp = LA3005 high pigment mutant; lp = LA3617 low pigment mutant. The colors indicate the deviation from the mean expression level for each gene, represented by bars. A red color signifies an increase in expression more than twice the average. A white color denotes no significant change from the average. A blue color represents a decrease in expression more than twice the average.