The complete chloroplast genome sequence of Cunninghamia lanceolata

Effects of Exponential N Application on Soil Exchangeable Base Cations and the Growth and Nutrient Contents of Clonal Chinese Fir Seedlings

Nitrogen (N) is an essential macronutrient for plant function and growth and a key component of amino acids, which form the building blocks of plant proteins and enzymes. However, misuse and overuse of N can have many negative impacts on the ecosystem, such as reducing soil exchangeable base cations (BCs) and causing soil acidification. In this research, we evaluated clonal Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) seedlings grown with exponentially increasing N fertilization (0, 0.5, 1, 2 g N seedling^-1) for a 100-day trial in a greenhouse. The growth of seedlings, their nutrient contents, and soil exchangeable cations were measured. We found that N addition significantly increased plant growth and N content but decreased phosphorous (P) and potassium (K) contents in plant seedlings. The high nitrogen (2 g N seedling^-1) treated seedlings showed a negative effect on growth, indicating that excessive nitrogen application caused damage to the seedlings. Soil pH, soil exchangeable base cations (BCs), soil total exchangeable bases (TEB), soil cation exchange capacity (CEC), and soil base saturation (BS) significantly decreased following N application. Our results implied that exponential fertilization resulted in soil acidification and degradation of soil capacity for supplying nutrient cations to the soil solution for plant uptake. In addition, the analysis of plants and BCs revealed that Na⁺ is an important base cation for BCs and for plant growth in nitrogen-induced acidified soils. Our results provide scientific insights for nitrogen application in seedling cultivation in soils and for further studies on the relationship between BCs and plant growth to result in high-quality seedlings while minimizing fertilizer input and mitigating potential soil pollution.

Exploring the Cunninghamia lanceolata(Lamb.) Hook Genome by BAC Sequencing

Cunninghamia lanceolata (Lamb.)Hook is an important economic timber tree in China. However, its genome characteristics have not been extensively assessed. To better understand its genome information, the bacterial artificial chromosome (BAC) library of chinese fir was constructed. A total of 422 BAC clones were selected and divided into 10 pools and sequenced, and with an average insert size of 121 kb, ranging from 97 to 145 kb. A total of 61,902,523 bp of reference sequences were sequenced and assembled, and based on an estimated genome size of 11.6 Gb for Chinese fir, the BAC library was estimated to have a total coverage of 0.53% genome equivalents. Bioinformatics analyses were also performed for repeated sequences, tRNAs, coding gene prediction, and functional annotation. The results of this study provide insights into the brief structure of the Chinese fir genome and has generated gene data that will facilitate molecular investigations on the mechanisms underlying tree growth.

Comparative Analysis of the Chloroplast Genomic Information of Cunninghamia lanceolata (Lamb.) Hook with Sibling Species from the Genera Cryptomeria D. Don, Taiwania Hayata, and Calocedrus Kurz

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is an important coniferous tree species for timber production, which accounts for ~40% of log supply from plantations in southern China. Chloroplast genetic engineering is an exciting field to engineer several valuable tree traits. In this study, we revisited the published complete Chinese fir (NC_021437) and four other coniferous species chloroplast genome sequence in Taxodiaceae. Comparison of their chloroplast genomes revealed three unique inversions found in the downstream of the gene clusters and evolutionary divergence were found, although overall the chloroplast genomic structure of the Cupressaceae linage was conserved. We also investigated the phylogenetic position of Chinese fir among conifers by examining gene functions, selection forces, substitution rates, and the full chloroplast genome sequence. Consistent with previous molecular systematics analysis, the results provided a well-supported phylogeny framework for the Cupressaceae that strongly confirms the “basal” position of Cunninghamia lanceolata. The structure of the Cunninghamia lanceolata chloroplast genome showed a partial lack of one IR copy, rearrangements clearly occurred and slight evolutionary divergence appeared among the cp genome of C. lanceolata, Taiwania cryptomerioides, Taiwania flousiana, Calocedrus formosana and Cryptomeria japonica. The information from sequence divergence and length variation of genes could be further considered for bioengineering research.