Photoprotective Effects of D1 Protein Turnover and the Lutein Cycle on Three Ephemeral Plants under Heat Stress

To clarify the characteristics of photoinhibition and the primary defense mechanisms of ephemeral plant leaves against photodestruction under high temperature stress,inhibitors and the technology to determine chlorophyll fluorescence were used to explore the protective effects of D1 protein turnover and the lutein cycle in the high temperature stress of the leaves of three ephemeral plants.The results showed that the maximum light conversion efficiency(Fv/Fm)of the ephemeral plant leaves decreased,and the initial fluorescence(Fo)increased under 35℃±1℃ heat stress for 1-4 h or on sunny days in the summer.Both Fv/Fm and Fo could be recovered after 8 h of darkness or afternoon weakening of the external temperature.Streptomycin sulfate(SM)or dithiothreitol(DTT)accelerated the decrease of Fv/Fm and the photochemical quenching coefficient(qP)in the leaves of three ephemeral plants at high temperature,and the decrease was greater in the SM than in the DTT treatment.When the high temperature stress was prolonged,the Y(II)values of light energy distribution parameters of PSII decreased,and the Y(NPQ)and Y(NO)values increased gradually in all the treatment groups of the three ephemeral plants.The results showed that the leaves of the three ephemeral plants had their own highly advanced mechanisms to protect against photodamage,which inhibited the turnover of D1 protein and xanthophyll cycle.This can damage the PSII reaction center in the leaves of the three ephemeral plants under high temperature.The protective effect of D1 protein turnover on heat stress in Erodium oxyrrhynchum and Senecio subdentatus was greater than that of the lutein cycle,while the protective effect of lutein cycle was greater than that of D1 protein turnover in Heliotropium acutiflorum subjected to heat damage.

The Photomorphogenic Central Repressor COP1: Conservation and Functional Diversification during Evolution

Green plants on the earth have evolved intricate mechanisms to acclimatize to and utilize sunlight.In Arabidopsis,light signals are perceived by photoreceptors and transmitted through divergent but overlapping signaling networks to modulate plant photomorphogenic development.COP1(CONSTITUTIVE PHOTOMORPHOGENIC 1)was first cloned as a central repressor of photomorphogenesis in higher plants and has been extensively studied for over 30 years.It acts as a RING E3 ubiquitin ligase downstream of multiple photoreceptors to target key light-signaling regulators for degradation,primarily as part of large protein complexes.The mammalian counterpart of COP1 is a pluripotent regulator of tumorigenesis and metabolism.A great deal of information on COP1 has been derived from whole-genome sequencing and functional studies in lower green plants,which enables us to illustrate its evolutionary history.Here,we reviewthe current understanding about COP1,with a focus on the conservation and functional diversification of COP1 and its signaling partners in different taxonomic clades.