Transcriptome analysis reveals rootstock-driven effects on growth and photosynthesis in Camellia chekiangoleosa: A phenotypic and biochemical perspective

Abstract

Camellia chekiangoleosa is a significant oil-bearing tree species, known for its high oleic acid content and shorter reproductive cycle compared to traditional oil-tea plants. However, there are few studies on the molecular mechanism and compatibility of the interaction between oil-Camellia scion and rootstock, which poses certain challenges to the cultivation and promotion of oil-Camellia. This study systematically evaluates the effects of hetero-grafting Camellia chekiangoleosa scions onto divergent rootstocks (Camellia chekiangoleosa, Camellia oleifera, and Camellia yuhsienensis). Then the research investigates how rootstock selection alters scion growth and development through phenotypic, biochemical, and transcriptomic analyses. Our findings reveal that the combination of C. oleifera scion grafted onto C. yuhsienensis suppresses auxin (IAA) and cytokinin (ZR) levels while elevating abscisic acid (ABA). Transcriptomic analysis identified that the PYL1, AMY, and INV1 screened by transcriptome data were mainly enriched in starch and sucrose metabolic pathways and plant hormone signal transduction, which collectively prioritize carbon allocation toward growth over storage. Meanwhile, hetero-grafting improved photosynthetic capacity by upregulating light-harvesting complex (LHC) genes and carotenoid biosynthesis enzymes (ZEP), optimizing light energy conversion and photoprotection. These findings provide novel insights into the molecular mechanisms underlying rootstock-scion interactions in oil-Camellia, bridging a critical knowledge gap in this economically important genus.

Fig 1. Concentration of ABA (A), IAA (B), ZR (C) and GA₃ (D) in leaves.

Co, C. oleifera. Cy, C.yuhsienensis. Cc, C. chekiangoleosa. ABA, abscisic acid. IAA, indole acetic acid. ZR, trans-Zeatin-riboside. GA₃, gibberellic acid. The bars indicate means ± SE (n = 3). Different letters on the bars indicate significant differences (P < 0.05) based on multiple comparisons (Duncan test) in ANOVA.

Fig 2. Content of starch (A), soluble sugar (B), carotenoid (C), and chlorophyll (D) in leaves.

The bars indicate means ± SE (n = 12). Different letters on the bars indicate significant differences (P < 0.05) based on multiple comparisons (Duncan test) in ANOVA.

Fig 3. Identification of up- and down regulated differentially expressed genes (DEGs) in comparisons.

The volcano plot shows the distribution of genes and the results of significant differences in genes. (A) Cc/Co group vs Cc/Cc group; (B) Cc/Cy group vs Cc/Cc group; (C) The number of DEPs between groups; (D) Venn diagram showing the number of genes differing between comparison groups, and the overlap between comparison groups. Up- and down-regulated genes are in red and blue, respectively.

Fig 4. The top 20 of KEGG enrichment pathways of the DEGs in (A) RCo vs. RCc and (B) RCy vs RCc KEGG analysis.

KEGG enrichment terms with q-value ≤0.05 were believed to be significantly enriched.

Fig 5. Genes network regulating starch and sucrose metabolism.

(A) Map of starch and sucrose metabolic pathway in both hetero-grafted seedlings. Gene-specific information is presented in S4 Table. (B) Heatmap of DEGs associated with starch and sucrose metabolism. Genes expression was based on mean FPKM value from three biological replicates, which were log2 transformed and normalized.