Molecular and Photosynthetic Performance in the Yellow Leaf Mutant of Torreya grandis According to Transcriptome Sequencing, Chlorophyll a Fluorescence, and Modulated 820 nm Reflection

Abstract

To study the photosynthetic energy mechanism and electron transfer in yellow leaves, transcriptomics combined with physiological approaches was used to explore the mechanism of the yellow leaf mutant Torreya grandis ‘Merrillii’. The results showed that chlorophyll content, the maximal photochemical efficiency of PSII (Fv/Fm), and the parameters related to the OJ phase of fluorescence (φEo, φRo) were all decreased significantly in mutant-type T. grandis leaves. The efficiency needed for an electron to be transferred from the reduced carriers between the two photosystems to the end acceptors of the PSI (δRo) and the quantum yield of the energy dissipation (φDo) were higher in the leaves of mutant-type T. grandis compared to those in wild-type leaves. Analysis of the prompt fluorescence kinetics and modulated 820 nm reflection showed that the electron transfer of PSII was decreased, and PSI activity was increased in yellow T. grandis leaves. Transcriptome data showed that the unigenes involved in chlorophyll synthesis and the photosynthetic electron transport complex were downregulated in the leaves of mutant-type T. grandis compared to wild-type leaves, while there were no observable changes in carotenoid content and biosynthesis. These findings suggest that the downregulation of genes involved in chlorophyll synthesis leads to decreased chlorophyll content, resulting in both PSI activity and carotenoids having higher tolerance when acting as photo-protective mechanisms for coping with chlorophyll deficit and decrease in linear electron transport in PSII.

Enhanced Salt Tolerance of Torreya grandis Genders Is Related to Nitric Oxide Level and Antioxidant Capacity

“…Torreya grandis is in a genus of deciduous conifer trees and is valued for its production of nuts and timber in China, but its distribution is limited by its cultivated area and prevailing weather conditions ( Hu et al, 2022 ; Shen et al, 2022 ). Many studies have investigated bioactive substance synthesis and efficacy ( Hu et al, 2022 ; Song et al, 2022 ) and the interactions of functional trait × environment interactions, such as the effect of salt stress on the photosynthetic activity of T. grandis ( Li et al, 2014 ).…”

Differences in gas exchange, chlorophyll fluorescence, and modulated reflection of light at 820 nm between two rhododendron cultivars under aluminum stress conditions

“…Under Al stress, the increase in V ox meant that the oxidation rate of PC and P 700 increased. The decrease in V red meant that the re-reduction rates of P 700 + and PC + decreased, which was related to the suppression of PSI, possibly because an insufficient number of electrons were transferred to PSI during the Al stress treatment [ 33 , 36 ]. In addition, after Al stress, compared with Kangnaixin, the V ox of Baijinpao had no significantly change, while the V red of Baijinpao was significantly decreased ( Fig 8 ).…”

“…For the simultaneous measurements, the light–dark transition was completed at 300 μs after the exposure, with PF and MR 820nm signals recorded under light and then DF signals recorded in darkness. The wavelengths were 627±10 nm for the actinic light LED, 820±25 nm for the modulated light LED and 735±15 nm for the far-red light LED [ 14 , 33 ]. Data were recorded with a variable rate: every 0.01ms from 0.01 to 0.3 ms, every 0.1ms from 0.3 to 3 ms, every 1 ms from 3 to 30 ms, every 10 ms from 30 to 300 ms, every 100 ms from 300 to 1000 ms [ 14 , 33 ].…”

“…The wavelengths were 627±10 nm for the actinic light LED, 820±25 nm for the modulated light LED and 735±15 nm for the far-red light LED [ 14 , 33 ]. Data were recorded with a variable rate: every 0.01ms from 0.01 to 0.3 ms, every 0.1ms from 0.3 to 3 ms, every 1 ms from 3 to 30 ms, every 10 ms from 30 to 300 ms, every 100 ms from 300 to 1000 ms [ 14 , 33 ].…”

“…Concurrent measurements of PF, DF, and MR 820nm can yield complementary and parallel data regarding the composition or operation of the photosynthetic machinery [ 32 ]. Currently, the techniques have commonly been used in forestry [ 33 ], agriculture [ 34 ], horticulture [ 35 ], and other fields [ 36 ].…”