Transcriptome-Wide Identification of TCP Transcription Factor Family Members in Pinus massoniana and Their Expression in Regulation of Development and in Response to Stress.

Pinus massoniana is an important coniferous tree species for barren mountain afforestation with enormous ecological and economic significance. It has strong adaptability to the environment. TEOSINTE BRANCHED 1/CYCLOIDEA/PCF (TCP) transcription factors (TFs) play crucial roles in plant stress response, hormone signal transduction, and development processes. At present, TCP TFs have been widely studied in multiple plant species, but research in P. massoniana has not been carried out. In this study, 13 PmTCP TFs were identified from the transcriptomes of P. massoniana. The phylogenetic results revealed that these PmTCP members were divided into two categories: Class I and Class II. Each PmTCP TF contained a conserved TCP domain, and the conserved motif types and numbers were similar in the same subgroup. According to the transcriptional profiling analysis under drought stress conditions, it was found that seven PmTCP genes responded to drought treatment to varying degrees. The qRT-PCR results showed that the majority of PmTCP genes were significantly expressed in the needles and may play a role in the developmental stage. Meanwhile, the PmTCPs could respond to several stresses and hormone treatments at different levels, which may be important for stress resistance. In addition, PmTCP7 and PmTCP12 were nuclear localization proteins, and PmTCP7 was a transcriptional suppressor. These results will help to explore the regulatory factors related to the growth and development of P. massoniana, enhance its stress resistance, and lay the foundation for further exploration of the physiological effects on PmTCPs.

Cloning of PmMYB6 in Pinus massoniana and an Analysis of Its Function.

Phenylpropanoids are crucial for the growth and development of plants and their interaction with the environment. As key transcriptional regulators of plant growth and development, MYB-like transcription factors play a vital role in the biosynthesis of phenylpropanoid metabolites. In this study, we functionally characterized PmMYB6, a Pinus massoniana gene that encodes an R2R3-MYB transcription factor. It was confirmed by qPCR that PmMYB6 was highly expressed in the flowers, xylem, and phloem of P. massoniana. By overexpressing PmMYB6 in tobacco and poplar, we found that transgenic plants had enlarged xylem, increased content of lignin and flavonoids, and up-regulated expression of several enzyme genes of the phenylpropane metabolism pathway to different degrees. The above research results indicate that PmMYB6 is involved in the metabolic flux distribution of different branches of the phenylpropane metabolic pathway, and the results may provide clues for the regulation of metabolic fluxes between flavonoids and the lignin biosynthesis pathways of P. massoniana, as well as provide a basis for the molecular breeding of P. massoniana.

Transcriptome-Wide Identification of the GRAS Transcription Factor Family in Pinus massoniana and Its Role in Regulating Development and Stress Response.

Pinus massoniana is a species used in afforestation and has high economic, ecological, and therapeutic significance. P. massoniana experiences a variety of biotic and abiotic stresses, and thus presents a suitable model for studying how woody plants respond to such stress. Numerous families of transcription factors are involved in the research of stress resistance, with the GRAS family playing a significant role in plant development and stress response. Though GRASs have been well explored in various plant species, much research remains to be undertaken on the GRAS family in P. massoniana. In this study, 21 PmGRASs were identified in the P. massoniana transcriptome. P. massoniana and Arabidopsis thaliana phylogenetic analyses revealed that the PmGRAS family can be separated into nine subfamilies. The results of qRT-PCR and transcriptome analyses under various stress and hormone treatments reveal that PmGRASs, particularly PmGRAS9, PmGRAS10 and PmGRAS17, may be crucial for stress resistance. The majority of PmGRASs were significantly expressed in needles and may function at multiple locales and developmental stages, according to tissue-specific expression analyses. Furthermore, the DELLA subfamily members PmGRAS9 and PmGRAS17 were nuclear localization proteins, while PmGRAS9 demonstrated transcriptional activation activity in yeast. The results of this study will help explore the relevant factors regulating the development of P. massoniana, improve stress resistance and lay the foundation for further identification of the biological functions of PmGRASs.

The Transcriptomic Analysis of the Response of Pinus massoniana to Drought Stress and a Functional Study on the ERF1 Transcription Factor.

Pinus massoniana is a major fast-growing timber tree species planted in arid areas of south China, which has a certain drought-resistant ability. However, severe drought and long-term water shortage limit its normal growth and development. Therefore, in this study, physiological indices, and the transcriptome sequencing and cloning of AP2/ERF transcription factor of P. massonsiana were determined to clarify its molecular mechanism of drought stress. The results showed that stomatal conductance (Gs) content was significantly decreased, and superoxide dismutase (SOD) activity, and malondialdehyde (MDA) and abscisic acid (ABA) content were significantly increased under drought stress. Transcriptomic analysis revealed that compared to the control, 9, 3550, and 4142 unigenes with differential expression were identified by comparing plants subjected to light, moderate or severe drought. AP2/ERF with high expression was screened out for cloning. To investigate the biological functions of ERF1, it was over-expressed in wild-type Populus davdianaand × P. bolleana via the leaf disc method. Under drought stress, compared to wild-type plants, ERF1 over-expressing poplar lines (OE) maintained a higher photosynthetic rate and growth, while the transpiration rate and stomatal conductance significantly decreased and water use efficiency was improved, indicating that drought tolerance was enhanced. This study provides an insight into the molecular mechanism of drought stress adaptation in P. massoniana.

Transcriptome-Wide Identification of CCCH-Type Zinc Finger Proteins Family in Pinus massoniana and RR-TZF Proteins in Stress Response.

CCCH-type zinc finger proteins play an important role in multiple biotic and abiotic stresses. More and more reports about CCCH functions in plant development and stress responses have appeared over the past few years, focusing especially on tandem CCCH zinc finger proteins (TZFs). However, this has not been reported in Pinaceae. In this study, we identified 46 CCCH proteins, including 6 plant TZF members in Pinus massoniana, and performed bioinformatic analysis. According to RT-PCR analysis, we revealed the expression patterns of five RR-TZF genes under different abiotic stresses and hormone treatments. Meanwhile, tissue-specific expression analysis suggested that all genes were mainly expressed in needles. Additionally, RR-TZF genes showed transcriptional activation activity in yeast. The results in this study will be beneficial in improving the stress resistance of P. massoniana and facilitating further studies on the biological and molecular functions of CCCH zinc finger proteins.