Enhancement of susceptivity to photoinhibition and photooxidation in rice chlorophyll b-less mutants

Abstract

Two rice chlorophyll (Chl) b-less mutants (VG28-1, VG30-5) and the respective wild type (WT) plant (cv. Zhonghua No. 11) were analyzed for the changes in Chl fluorescence parameters, xanthophyll cycle pool, and its de-epoxidation state under exposure to strong irradiance, SI (1 700 μmol m −2 s −1 ). We also examined alterations in the chloroplast ultrastructure of the mutants induced by methyl viologen (MV) photooxidation. During HI (0−3.5 h), the photoinactivation of photosystem 2 (PS2) appeared earlier and more severely in Chl b-less mutants than in the WT. The decreases in maximal photochemical efficiency of PS2 in the dark (F v /F m ), quantum efficiency of PS2 electron transport (Ф PS2 ), photochemical quenching (q P ), as well as rate of photochemistry (P rate ), and the increases in de-epoxidation state (DES) and rate of thermal dissipation of excitation energy (D rate ) were significantly greater in Chl b-mutants compared with the WT plant. A relatively larger xanthophyll pool and 78−83 % conversion of violaxanthin into antheraxanthin and zeaxanthin in the mutants after 3.5 h of HI was accompanied with a high ratio of inactive/total PS2 (0.55−0.73) and high 1 − q P (0.57−0.68) which showed that the activities of the xanthophyll cycle were probably insufficient to protect the photosynthetic apparatus against photoinhibition. No apparent difference of chloroplast ultrastructure was found between Chl b-less mutants and WT plants grown under low, LI (180 μmol m −2 s −1 ) and high, HI (700 μmol m −2 s −1 ) irradiance. However, swollen chloroplasts and slight dilation of thylakoids occurred in both mutants and the WT grown under LI followed by MV treatment. These typical symptoms of photooxidative damage were aggravated as plants were exposed to HI. Distorted and loose scattered thylakoids were observed in particular in the Chl b-less mutants. A greater extent of photoinhibition and photooxidation in these mutants indicated that the susceptibility to HI and oxidative stresses was enhanced in the photosynthetic apparatus without Chl b most likely as a consequence of a smaller antenna size.Additional key words: chlorophyll fluorescence; chloroplast ultrastructure; high and low irradiance; methyl viologen; Oryza; xanthophyll cycle pool.

Light acclimation and HSO3 − damage on photosynthetic apparatus of three subtropical forest species

“…A. acuminatissima as a mesophytes species had a large-scale feasible growing light intensities with a significant decrease of RLC after growing with overshadow treatment. The amount of acceptors or donors nearby P 680 of tested plant was supposed to be reduced and resulted in lessening the function of PSII in accepting light energy and transferring electron (Demmig-Adams and Adams 1992; Lin et al 2009). When treated by NaHSO 3 , relative electron transport rate of PSII (ETR) and actual photochemical efficiency of PS II (DF/Fm 0 ) were extremely affected in P. massoniana needles.…”

“…As to the thylakoid membrane organization and function, light has long been considered as the most important modifying factor (González et al 1993;Moharekar et al 2007). Growing with different light exposures determined the electron transport ability of chloroplast, the stacking density and grana size in thylakoid (Anderson 1986;Lin et al 2009). Here, Grown under 12% natural light resulted in a more compact thylakoid stacking structure in three species for providing more light harvesting complexes in PSII in order to effectively utilize the limited light energy.…”

An Appraisal on the Source-to-Sink Relationship in Plants: an Application of Desorption Electrospray Ionization Mass Spectrometry Imaging

“…1,3 The connection between mature and young leaves (net exporters and importers of biosynthesized nutrients, respectively) is usually called source-to-sink relationship and occurs through the phloem. [2][3][4][5][6][7][8] When young leaves import amino acids and ureides from the roots, the connection is usually called root-to-shoot transportation and occurs via the xylem. 3 Studies on the synthesis, mobility and storage of metabolites within plants have been conducted for decades.…”

Fine mapping and photosynthetic characteristics of the lower chlorophyll b 1 mutant in rice (Oryza sativa L.)

“…, Lin et al. ). In this study, the lcb1 mutant showed a significantly decreased chlorophyll b content and a Chl a/b ratio of almost 10; therefore, it is a low chlorophyll b mutant (Terao et al.…”