Transcriptome Analysis of Cambium Tissue of Paulownia Collected during Winter and Spring

Abstract

Paulownia (Paulownia elongata) is a fast-growing, multipurpose deciduous hardwood species that grows in a wide range of temperatures from –30 °C to 45 °C. Seasonal cues influence the secondary growth of tree stems, including cambial activity, wood chemistry, and transition to latewood formation. In this study, a de novo transcriptome approach was conducted to identify the transcripts expressed in vascular cambial tissue from senescent winter and actively growing spring seasons. An Illumina paired-end sequenced cambial transcriptome generated 297,049,842 clean reads, which finally yielded 61,639 annotated unigenes. Based on non-redundant protein database analyses, Paulownia cambial unigenes shared the highest homology (64.8%) with Erythranthe guttata. KEGG annotation of 35,471 unigenes identified pathways enriched in metabolic activities. Transcriptome-wide DEG analysis showed that 2688 and 7411 genes were upregulated and downregulated, respectively, in spring tissues compared to winter. Interestingly, several transcripts encoding heat shock proteins were upregulated in the spring season. RT-qPCR expression results of fifteen wood-forming candidate genes involved in hemicellulose, cellulose, lignin, auxin, and cytokinin pathways showed that the hemicellulose genes (CSLC4, FUT1, AXY4, GATL1, and IRX19) were significantly upregulated in spring season tissues when compared to winter tissues. In contrast, lignin pathway genes CCR1 and CAD1 were upregulated in winter cambium. Finally, a transcriptome-wide marker analysis identified 11,338 Simple Sequence Repeat (SSRs). The AG/CT dinucleotide repeat predominately represented all SSRs. Altogether, the cambial transcriptomic analysis reported here highlights the molecular events of wood formation during winter and spring. The identification of candidate genes involved in the cambial growth provides a roadmap of wood formation in Paulownia and other trees for the seasonal growth variation.

Liana Attachment to Supports Leads to Profound Changes in Xylem Anatomy and Cambium and Differentiating Xylem Transcriptional Profile

“…To comprehend the transcriptional control mechanism responsible for the concomitant formation of the selfsupporting and lianescent xylem in different portions of the same plant of B. magnifica , we sampled the cambium and differentiating xylem of entire internodes samples (approximately 30 cm long) collected from 60 cm from the shoot apex to the base of the stem (from around the 10 th to the 20 th internodes), along different stems of a single plant. After two years of cultivation, the sampling was conducted in April 2018 during the period of active cambium by peeling the bark and gently scraping the exposed xylem (Allona et al , 1998;Sterky et al , 1998;Perry et al , 2021). The cambial activity was assessed by anatomical analysis (Supporting Information Fig.…”