Abstract
Low-temperature stress is the main limiting factor of cucurbit crop cultivation as it affects crop yield and quality. The identification of genes involved in cold tolerance is a crucial aspect of pumpkin rootstock breeding. Here, we examined the function of a pumpkin Regulator of Chromosome Condensation 1 (CmRCC1) gene in the root development and cold stress responses of tobacco (Nicotiana benthamiana). CmRCC1 expression was differentially induced in pumpkin root, stem, and leaf under cold stress. Transient transformation showed that CmRCC1 is located in the nucleus. CmRCC1 overexpression in tobacco increased the gravitropic set-point angle in lateral roots, as well as root diameter and volume. The expression of auxin polar transport factors, PIN1 and PIN3, decreased and increased in CmRCC1-overexpressed plants, respectively. Yeast two-hybrid verification and luciferase complementation imaging assay showed that CmRCC1 interacts with CmLAZY1. Furthermore, the decreases in maximum quantum yield of PS II, the effective quantum yield of PS II, and electron transfer rate and the increases in quantum yield of nonregulated energy dissipation and malondialdehyde content were compromised in transgenic plants compared with wild-type plants under cold stress. The results suggest that CmRCC1 plays an important role in the regulation of root architecture and positively modulates cold tolerance.
Highlights
The Regulator of Chromosome Condensation 1 (RCC1) superfamily of proteins is characterized by 350–500 residue domain, known as the RCC1-like domain (RLD), which was first reported in human RCC1 in 1987 (Ohtsubo et al, 1987)
The phylogenetic tree built from the alignment of CmRCC1 with the previously identified Arabidopsis RCC1s revealed the evolutionary distances between the sequences (Figure 1A)
The GFP-CmRCC1 fusion construct and GFP control in the pCAMBIA1305.4-N-GFP vector driven by CaMV35S promoter were transiently expressed in tobacco epidermal cells and visualized under a laser scanning confocal microscope to determine the subcellular localization of CmRCC1
Summary
The Regulator of Chromosome Condensation 1 (RCC1) superfamily of proteins is characterized by 350–500 residue domain, known as the RCC1-like domain (RLD), which was first reported in human RCC1 in 1987 (Ohtsubo et al, 1987). RCC1 consists of seven homologous repeats of 51–68 amino acid residues It combines with chromatin and a nuclear Ras-like G protein, Ran, to establish a RanGTP concentration gradient, which affects the formation and function of the nuclear envelope, spindle formation, nuclear transport, and the cell cycle during tumorigenesis (Ren et al, 2020). Since the initial identification of RCC1, a number of proteins that contain one or more RLDs have been discovered The Tolerant to Chilling and Freezing 1 (TCF1) gene in Arabidopsis encodes a protein containing six predicted tandem RCC1 repeats that show a similarity to yeast and human RCC1 (Ohtsubo et al, 1989; Renault et al, 1998). 56 RCC1 genes have been identified in upland cotton (Gossypium hirsutum), among which Gh_A05G3028 and Gh_D10G2310, the homologous genes of AtTCF1 and AtUVR8, were dramatically induced under salt treatment, and the silencing of these two genes exhibited a salt-sensitive phenotype (Liu et al, 2019)
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