Identification of CDPK Gene Family in Solanum habrochaites and Its Function Analysis under Stress

Whole-Genome Identification of Regulatory Function of CDPK Gene Families in Cold Stress Response for Prunus mume and Prunus mume var. Tortuosa

Calcium-dependent protein kinases (CDPK) are known to mediate plant growth and development and respond to various environmental changes. Here, we performed whole-genome identification of CDPK families in cultivated and wild mei (Prunus mume). We identified 14 and 17 CDPK genes in P. mume and P. mume var. Tortuosa genomes, respectively. All 270 CPDK proteins were classified into four clade, displaying frequent homologies between these two genomes and those of other Rosaceae species. Exon/intron structure, motif and synteny blocks were conserved between P. mume and P. mume var. Tortuosa. The interaction network revealed all PmCDPK and PmvCDPK proteins is interacted with respiratory burst oxidase homologs (RBOHs) and mitogen-activated protein kinase (MAPK). RNA-seq data analysis of cold experiments show that cis-acting elements in the PmCDPK genes, especially PmCDPK14, are associated with cold hardiness. Our results provide and broad insights into CDPK gene families in mei and their role in modulating cold stress response in plants.

An R2R3-MYB network modulates stem strength by regulating lignin biosynthesis and secondary cell wall thickening in herbaceous peony

Stem strength is an important agronomic trait affecting plant lodging, and plays an essential role in the quality and yield of plants. Thickened secondary cell walls in stems provide mechanical strength that allows plants to stand upright, but the regulatory mechanism of secondary cell wall thickening and stem strength in cut flowers remains unclear. In this study, first, a total of 11 non-redundant Paeonia lactiflora R2R3-MYBs related to stem strength were identified and isolated from cut-flower herbaceous peony, among which PlMYB43, PlMYB83 and PlMYB103 were the most upregulated differentially expressed genes. Then, the expression characteristics revealed that these three R2R3-MYBs were specifically expressed in stems and acted as transcriptional activators. Next, biological function verification showed that these P. lactiflora R2R3-MYBs positively regulated stem strength, secondary cell wall thickness and lignin deposition. Furthermore, yeast-one-hybrid and dual luciferase reporter assays demonstrated that they could bind to the promoter of caffeic acid O-methyltransferase gene (PlCOMT2) and/or laccase gene (PlLAC4), two key genes involved in lignin biosynthesis. In addition, the function of PlLAC4 in increasing lignin deposition was confirmed by virus-induced gene silencing and overexpression. Moreover, PlMYB83 could also act as a transcriptional activator of PlMYB43. The findings of the study propose a regulatory network of R2R3-MYBs modulating lignin biosynthesis and secondary cell wall thickening for improving stem lodging resistance, and provide a resource for molecular genetic engineering breeding of cut flowers.

Genome-wide identification of the CPK gene family in wheat (Triticum aestivum L.) and characterization of TaCPK40 associated with seed dormancy and germination

Calcium-dependent protein kinases (CPKs), important sensors of calcium signals, play an essential role in plant growth, development, and stress responses. Although the CPK gene family has been characterized in many plants, the functions of the CPK gene family in wheat, including their relationship to seed dormancy and germination, remain unclear. In this study, we identified 84 TaCPK genes in wheat (TaCPK1-84). According to their phylogenetic relationship, they were divided into four groups (I-IV). TaCPK genes in the same group were found to have similar gene structures and motifs. Chromosomal localization indicated that TaCPK genes were unevenly distributed across 21 wheat chromosomes. TaCPK gene expansion occurred through segmental duplication events and underwent strong negative selection. A large number of cis-regulatory elements related to light response, phytohormone response, and abiotic stress response were identified in the upstream promoter sequences of TaCPK genes. TaCPK gene expression was found to be tissue- and growth-stage-diverse. Analysis of the expression patterns of several wheat varieties with contrasting seed dormancy and germination phenotypes resulted in the identification of 11 candidate genes (TaCPK38/-40/-43/-47/-50/-60/-67/-70/-75/-78/-80) which are likely associated with seed dormancy and germination. The ectopic expression of TaCPK40 in Arabidopsis promoted seed germination and reduced abscisic acid (ABA) sensitivity during germination, indicating that TaCPK40 negatively regulates seed dormancy and positively regulates seed germination. These findings advance our understanding of the multifaceted functions of CPK genes in seed dormancy and germination, and provide potential candidate genes for controlling wheat seed dormancy and germination.

GhCDPK60 positively regulates drought stress tolerance in both transgenic Arabidopsis and cotton by regulating proline content and ROS level

Calcium-Dependent Protein Kinases (CDPKs) involved in regulating downstream components of calcium signaling pathways play a role in tolerance to abiotic stresses and seed development in plants. However, functions of only a few cotton CDPKs have been clarified at present. In this study, 80 conserved CDPKs in Gossypium hirsutum L. were identified and characterized, which was divided into four subgroups. Among them, the transcript level of GhCDPK60 was significantly upregulated under drought and several hormone treatments. And we found that the expression levels of several stress-inducible genes down-regulated in GhCDPK60-silence cotton and up-regulated in GhCDPK60-overexpressing Arabidopsis. In addition, physiological analyses demonstrated that GhCDPK60 improved drought stress tolerance by improving the osmotic adjustment ability and reducing the accumulation of reactive oxygen species (ROS) in plants. These findings broaden our understanding of the biological roles of GhCDPK60 and mechanisms underlying drought stress tolerance in cotton.

Transcription level differences in Taxus wallichiana var. mairei elicited by Ce3+, Ce4+ and methyl jasmonate

Taxol is a precious and effective anticancer drug. Cerium and methyl jasmonate (MJ) have been shown to increase the yield of taxol in taxus cells. However, the mechanisms of cerium-mediated and MJ-mediated taxol biosynthesis remain unknown. RNA-Seq was applied to study the overall regulation mechanism of cerium and MJ on taxol biosynthesis and analyze the differences among T. mairei cells elicited by Ce³⁺, Ce⁴⁺ and MJ on transcriptional level . Using sequence homology, 179 unigenes were identified as taxol synthesis genes. Under the condition of 100 μM MJ, taxol synthesis genes were up-regulated. Notably, taxol synthesis genes were down-regulated expression at 1 mM Ce³⁺ and 1 mM Ce⁴⁺. Differential expression genes involved in some related functions were analyzed, such as MAPK signaling pathway and plant-pathogen interaction. Sequence alignment and phylogenetic analysis of nine differentially expressed WRKYs in our data were carried out.