The photo-inhibition of camphor leaves (Cinnamomum camphora L.) by NaCl stress based on physiological, chloroplast structure and comparative proteomic analysis

Jiammin Yue; Dawei Shi; Liang Zhang; Zihan Zhang; Zhiyuan Fu; Qiong Ren; Jinchi Zhang

doi:10.7717/peerj.9443

The photo-inhibition of camphor leaves (Cinnamomum camphora L.) by NaCl stress based on physiological, chloroplast structure and comparative proteomic analysis

PeerJ. 2020 Aug 7:8:e9443. doi: 10.7717/peerj.9443. eCollection 2020.

Authors

Jiammin Yue^{1

2

3}, Dawei Shi¹, Liang Zhang¹, Zihan Zhang¹, Zhiyuan Fu¹, Qiong Ren⁴, Jinchi Zhang¹

Affiliations

¹ Co-Innovation Center for Sustainable Forestry in Southern China of Jiangsu Province & Key Laboratory of Soil and Water Conservation and Ecological Restoration, Nanjing Forestry University, Nanjing, Jiangsu, China.
² Key Laboratory of Land Degradation and Ecosystem Restoration & Key Laboratory of Rehabilitation and Reconstruction of Degraded Ecosystems in Northwest China, Ningxia University, Yingchuan, Ningxia, China.
³ Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada.
⁴ Jiangxi Academy of Forestry, Nanchang, China.

Abstract

Background: The distribution and use of camphor (Cinnamomum camphora L.) trees are constrained by increasing soil salinity in south-eastern China along the Yangtze River. However, the response mechanism of this species to salinity, especially in team of photosynthesis, are unknown.

Methods: Here, we analysed themorphological, physiological, ultrastructural, and proteomic traits of camphor seedlings under NaCl (103.45 mM) treatment in pot experiments for 80 days.

Results: The growth was limited because of photosynthetic inhibition, with the most significant disturbance occurring within 50 days. Salinity caused severe reductions in the leaf photosynthetic rate (A _n), stomatal conductance (g _s), maximal chlorophyll fluorescence (F_m), maximum quantum yield of PSII (F_v/F_m), non-photochemical quenching (NPQ), relative quantum efficiency of PSII photochemistry (ΦPSII), photochemical quenching coefficient (qP) and photo-pigment contents (chlorophyll a (Cha), chlorophyll b (Chb), total chlorophyll (Chl)); weakened the antioxidant effects, including those of malondialdehyde (MDA), superoxide dismutase (SOD) and peroxidase (POD); and injured chloroplasts. The physiologicalresults indicated that the main reason for photo-inhibition was oxidative factors induced by NaCl. The proteomic results based on isobaric tags for relative and absolute quantitation (iTRAQ) further confirmedthat photosynthesis was the most significant disrupted process by salinity (P < 0.01) and there were 30 downregulated differentially expression proteins (DEPs) and one upregulated DEP related to restraint of the photosynthetic system, which affected photosystem I, photosystem II, the Cytochrome b6/f complex, ATP synthase and the light-harvesting chlorophyll protein complex. In addition, 57 DEPs were related to photo-inhibition by redox effect and 6 downregulated DEPs, including O2 evolving complex 33kD family protein (gi-224094610) and five other predicted proteins (gi-743921083, gi-743840443, gi-743885735, gi-743810316 and gi-743881832) were directly affected. This study provides new proteomic information and explains the possible mechanisms of photo-inhibition caused by salinity on C. camphor.

Keywords: C. camphor; NaCl treatment; Oxidative stress; Photosynthetic inhibition; Proteomic analysis.

Grants and funding

This work was supported by the Jiangsu Agriculture Science and Technology Innovation Fund (Grant No. CX(17)1004), the National Special Fund for Forestry Scientific Research in the Public Interest (Grant No. 201504406), the Major Fund for Natural Science of Jiangsu Higher Education Institutions (Grant No. 15KJA220004), the National Foundation of Forestry Science and Technology Popularization (Grant No. [2015]17), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the Ningxia Autonomous Region Provincial Fund (2020AAC03091), and the Doctorate Fellowship Foundation of Nanjing Forestry University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.