Differences in leaf anatomy, photosynthesis, and photoprotective strategies in the yellow-green leaf mutant and wild type of Rosa beggeriana Schrenk

Abstract

Although the underlying mechanisms of chlorophyll biosynthesis have been intensively deciphered in model plants, leaf color mutants have not yet been fully studied in woody species. In this study, leaf anatomy, diurnal changes in photosynthesis and photoprotection were investigated in the yellow-green leaf (ygl) mutant of Rosa beggeriana. Chloroplast ultrastructure, pigment biosynthesis, and photosynthesis were impaired and led to photoinhibition at noon in the ygl mutant. The negative changes in leaf anatomy increased the risk of excess light absorption in the mutant. Moreover, the ygl mutant preferred to consume the excited energy through photorespiration rather than via heat dissipation. Finally, antioxidant defenses failed to scavenge reactive oxygen species and led to severe lipid peroxidation in the mutant. The results suggested that inhibition of photosynthesis in the ygl mutant of R. beggeriana was associated with the altered photoprotective strategies that involved in leaf anatomy, photorespiration, thermal dissipation, and antioxidant system.

Comparative Transcriptome Profiling Analysis Reveals the Adaptive Molecular Mechanism of Yellow-Green Leaf in Rosa beggeriana ‘Aurea’

“…To evaluate the effects of leaf mutation on chloroplast structure, the 2 mm × 2 mm pieces from uppermost leaf on the sunny side of an annual branch from WT and yl mutant plants were cut from leaves for SEM ( Figures 1B,C,E,F ). Then the leaf cut sections were fixed in 2.5% glutaraldehyde and 1% osmium tetroxide, dehydrated in a series of graded ethanol as previous description ( Yang et al, 2020 ). The samples were observed and photographed with a SEM SU-8010 (Hitachi Ltd., Tokyo, Japan).…”

“…The samples were observed and photographed with a SEM SU-8010 (Hitachi Ltd., Tokyo, Japan). Then, the stomatal density, chloroplast ultrastructure were measured and analyzed according to the previous description ( Yang et al, 2020 ).…”

“…Chlorophyll fluorescence parameters were measured as previous description ( Yang et al, 2020 ) with a portable fluorometer DAUL-PAM-100 (Walz, Effeltrich, Germany) at 12:00. The relative parameters of F V / F M , Y(II) photosystem II (PSII), ETR, Y(NO), Y(NPQ), qN, qP, and qL were calculated and analyzed ( Liu et al, 2019 ).…”

“…R. beggeriana ‘Aurea’ is a yl mutant and originated from R. beggeriana Schrenk by 60 Co-γ irradiation. It is the first yl mutant in the genus Rosa up to now and its cold resistant capability has not changed ( Huang et al, 2007 ; Yang et al, 2016 , 2020 ). R. beggeriana ‘Aurea’ was used as an important germplasm for innovation cultivars through interspecific hybridization with modern rose ( Yang et al, 2016 ).…”

“…Meanwhile, the photosynthesis efficiency, chlorophylls, and carotenoids accumulation were impaired ( Supplementary Table S1 and Supplementary Figure S1 ), which resulted in photoinhibition at noon in yl mutant. Photorespiration was stronger and lipid peroxidation was evoking to scavenge reactive oxygen for photoprotective strategies ( Yang et al, 2020 ). However, the underlying molecular mechanism for yl mutation is still unclear.…”