Response of Chinese fir seedlings to low phosphorus stress and analysis of gene expression differences

Chinese fir(Cunninghamia lanceolata) is an excellent fast-growing timber species occurring in southern China and has significant value in the forestry industry. In order to enhance the phosphorus utilization efficiency in Chinese fir, four clones named X6, S3, S39 and FK were used, and low phosphorus(LP) stress experiments were performed to analyze the response of different clones to phosphorus deficiency. According to the results on seedling height, maximum root length, leaf blade aspect ratio, root ratio, malondialdehyde content, acid phosphates activity,proline content, soluble protein level, and chlorophyll a and b levels of the tested clones, compared to the control groups(CK), the phosphorus high efficiency clone X6 was screen out for transcriptome sequencing experiments. De novo RNA-seq was then used to sequence the root transcriptomes of X6 under LP stress and CK, and we then compared the gene expression differences under the two conditions. A total of 3416 SDEGs were obtained by comparing the LP and CK groups, among which 1742 were up-regulated and 1682 were down-regulated. All SDEGs obtained from the LP and CK treated samples were subjected to KEGG annotation and classification. Through classification statistical analysis using WEGO software,607 SDEGs obtained KEGG pathway annotations, which were related to 206 metabolic pathways. In Chinese fir subjected to LP stress, 53 SDEGs related with phosphorus metabolism, and phosphate uptake and transport were obtained from our transcriptome data. Based on the phosphorus metabolism pathway obtained by KEGG classification, combined with previously report on gene annotation related with phosphorus metabolism, the enzymes encoded by SDEG related with phosphorus metabolism and their expression pattern were mapped onto phosphorus metabolism pathway.

Cloning and sequence analysis of nine novel MYB genes in Taxodiaceae plants

Myeloblastosis （MYB） is one of the largest transcribed factor families in plants. To gain an overall picture of the evolution of MYB genes in relict plants, we cloned nine novel MYB genes in Taxodiaceae plants （ Taxodium distichum, Taxodium ascendens, Cryptomeria japonica var. Sinensis, Cryptomeria japonica cv. Araucarioides, Cryptomer Ja- ponica, Metasequoia glyptostroboides, Cunninghamia lanceolata, Tai- wania cryptomerioides and Glyptostrobus pensilis）. The deduced amino acid sequences for MYBs showed that the nine MYB proteins contained two DNA binding domains. The first domain is from amino acid position 29 to 78, wherein three tryptophanes at 33, 53 and 73 were separated by 19 amino acids, respectively. The second domain is from amino acid position 82 to 127, wherein three tryptophanes at 86, 105 and 124 were separated by 18 amino acids, respectively, whereas the first tryptophane at amino acid position 86 is replaced by a phenylalanine. The characteri- zation of these conserved domains at nine MYBs indicated that they all belong to the R2R3-MYB group. The secondary structure analysis showed that a-helix and 13-turn are the major motifs of the predicted secondary structure of MYBs. The three dimensional model of each MYB protein showed that the structure is like clip, making it more flexi- ble and mobile. The similarities between the nine MYB proteins in Taxodiaceae were calculated. The highest identical value of 99% is be- tween CjsMYB, CjMYB and CjaMYB, whereas the lowest value of 82% is between TaMYB and C1MYB. According to the phylogenetic tree, the distances between different genera were relatively large whereas those within genera were relatively small. As expected, accessions of the same genus formed a subgroup before being grouped with other genera.