Plasma membrane intrinsic protein (PIP) is one of the largest subfamilies of Aquaporins (AQPs) and plays an important role in plant growth and development, and resistance to abiotic stress. In this study, the full length of the EuPIP1;1 cDNA was cloned from Eucommia ulmoides using the rapid amplification of cDNA ends (RACE) method. The EuPIP1;1 gene was induced by drought treatment and expressed in all tested tissues, with the highest expression level in fruit. The subcellular localization showed that EuPIP1;1 was located in the plasma membrane. Constitutive overexpression of EuPIP1;1 in Arabidopsisthaliana could promote leaf growth and development, and accelerate bolting and flowering. Six genes related to growth and flowering (AtPIF4, AtTCP14, AtCRY1, AtCRY2, AtFCA and AtFT) were significantly up-regulated in transgenic lines. Further, EuPIP1;1 gene improved resistance to drought and salt stress in transgenic Arabidopsis. Under drought and salt stress treatment, the transgenic lines had a higher germination rate and accumulation of osmotic substances, lower membrane damage, and could maintain ion homeostasis. Our results suggest that EuPIP1;1 plays an essential role in plant growth and development and in the response to drought and salt stress.

Growth-regulating factors (GRFs) are plant-specific transcription factors that play an important role in plant growth and development. In this study, fifteen GRF gene members containing QLQ and WRC domains were identified in Zanthoxylum armatum. Phylogenetic and collinearity analysis showed that ZaGRFs were closely related to CsGRFs and AtGRFs, and distantly related to OsGRFs. There are a large number of cis-acting elements related to hormone response and stress induction in the GRF gene promoter region of Z. armatum. Tissue-specific expression analysis showed that except for ZaGRF7, all the ZaGRFs were highly expressed in young parts with active growth and development, including terminal buds, seeds, and young flowers, suggesting their key roles in Z. armatum growth and development. Eight ZaGRFs were selected to investigate the transcriptional response to auxin, gibberellin and drought treatments. A total of six ZaGRFs in the NAA treatment, four ZaGRFs in the GA₃ treatment, and six ZaGRFs in the PEG treatment were induced and significantly up-regulated. Overexpression of ZaGRF6 increased branching and chlorophyll content and delayed senescence of transgenic Nicotiana benthamiana. ZaGRF6 increased the expression of CRF2 and suppressed the expression of ARR4 and CKX1, indicating that ZaGRF6 is involved in cytokinin metabolism and signal transduction. These research results lay a foundation for further analysis of the GRF gene function of Z. armatum and provide candidate genes for growth, development, and stress resistance breeding of Z. armatum.

Aquaporins are a specific type of membrane channel proteins that efficiently transport water molecules and other small molecular substrates in plants. In this study, we isolated the plasma membrane aquaporin gene EuPIP1;2 from Eucommia ulmoides, an important medicinal plant in China. The EuPIP1;2 protein was localized on the plasma membrane. Quantitative RT-PCR analysis revealed that EuPIP1;2 was constitutively expressed in all analyzed tissues, with the highest expression levels detected in the fruit and root. Overexpression of EuPIP1;2 in transgenic tobacco enhanced plant tolerance of drought and salinity. Under drought and salt stress, the transgenic lines exhibited higher percentage germination, longer roots, and enhanced percentage survival compared with wild-type plants. The contents of malonaldehyde and proline suggested that EuPIP1;2 improved drought and salt tolerance in transgenic lines by reducing damage to membranes and improving osmotic adjustment. We predict that EuPIP1;2 could be applied to improve drought and salt tolerance in transgenic plants.

PIN-formed (PIN) proteins are important auxin carriers that participate in the polar distribution of auxin in plants. In this study, 16 ZaPIN genes were identified from the whole genome of Zanthoxylum armatum DC. The physicochemical properties and structure of PIN proteins were determined, and the gene sequences and promoter regions were analyzed to identify cis-acting elements and conserved motifs. The transcript profiles of ZaPIN genes in different tissues and in response to auxin and gibberellin treatments were also analyzed. A phylogenetic analysis separated the 16 ZaPIN genes into four groups. The ZaPIN genes showed the closest evolutionary relationship to those of Citrus sinensis and the most distant evolutionary relationship to those of Oryza sativa. A cis-element analysis revealed a large number of cis elements in ZaPIN promoter regions related to plant hormones, plant growth and development, and stress stimuli, suggesting that ZaPINs have a wide range of biological activities. Additionally, gene expression profiling revealed that ZaPINs had different expression patterns in nine tissues. Further qRT-PCR analyses revealed that most ZaPINs were upregulated by auxin and gibberellin in young leaves. Our results provide useful information for further structural and functional analyses of the ZaPIN gene family in Z. armatum.