Plasma membrane intrinsic proteins (PIPs), as members of the aquaporin (AQPs) family, can transport not only water but also urea, CO₂, H₂O₂, metal ions, and trace elements. They are crucial for maintaining water balance, substance transport, and responding to various stresses. This article delves into the structure, function, response mechanism, molecular mechanism, and regulatory mechanism of PIPs as a result of biological and abiotic stresses. It also summarizes current research trends surrounding PIPs and highlights potential research directions for further exploration. The aim is to assist researchers in related fields in gaining a more comprehensive understanding and precise insight into the advancements in PIP research.

Sugarcane is an important sugar and energy crop in the world. Germplasm innovation is a significant way to breed breakthrough sugarcane varieties. Modern sugarcane varieties all contain the blood relationship of Saccharum officinarum and Saccharum spontaneum. High sugar results from S. officinarum and the resistance genes from S. spontaneum. In order to improve the sugarcane quality, breeders use S. officinarum and S. spontaneum to cross and obtain hybrid offspring with high sugar and high resistance. Therefore, the authenticity of S. officinarum and S. spontaneum progeny materials directly affects the efficiency of sugarcane breeding. In this study, the tetra-primer amplification hindered mutation system (ARMS PCR) was used to identify ten suspected S. officinarum and eleven suspected S. spontaneum germplasm materials, then further validated by chromosome counting and genome in situ hybridization (GISH). Among the ten suspected S. officinarum materials to be identified, three were real S. officinarum materials, they were 14NG124, 51NG103, and Guan A. Nine of the eleven suspected S. spontaneum to be identified were fake S. spontaneum materials, these were Yunge 2007-12-165, Guangxi 87-20, Yunnan 82-16, Yunge 2007-11, YNLC 16, Laos No. 2, Yunnan 82-29, 2015-83, and 2013-20. The ARMS PCR results were the same as the GISH results. The three real S. officinarum materials had 80 chromosomes. Using ARMS PCR and GISH, three S. officinarum and nine S. spontaneum materials were proven to be authentic. Through chromosome number statistics, it was found that the three real S. officinarum had 80 chromosomes. Authentic materials were identified and selected to enrich the genetic background of sugarcane through hybridization and reduce the influence on the breeding process of the misuse of fake S. officinarum and S. spontaneum.

Interspecific hybridization serves as a crucial strategy for innovating sugarcane germplasms. Currently, nearly all modern sugarcane varieties that incorporate genetic material are derived from Saccharum spontaneum. The number of chromosomes in S. spontaneum ranges from 40 to 128, contributing significantly to the diversity of its genetic resources. However, the genetic mechanisms driving chromosome number variation in S. spontaneum remain to be fully elucidated. Here, oligonucleotide fluorescence in situ hybridization (Oligo-FISH) was conducted to identify individual chromosomes and explore chromosome transmission during the intraspecific hybridization of S. spontaneum. The results indicate that from the progenies generated from S. spontaneum Yunnan2017-22 (2n = 8x = 64) and Yunnan82-1 (2n = 8x = 64) emerged two distinct karyotypes, 2n = 12x = 96 (A1) and 2n = 8x = 64 (A2, A33-1, A18). This implies that the chromosome inheritances were 2n + n and n + n in the progenies. However, self-pollinated samples of A1 (2n = 12x = 96) produced normal offspring C1 (2n = 94) and C2 (2n = 96). The 2n + n inheritance pattern did not continue. In another cross, the progenies derived from S. spontaneum Yunnan2017-41 (2n = 8x = 64) and Yunnan8 (2n = 10x = 80) carried a karyotype of 2n = 9x = 72, with n + n inheritance mode. These findings highlight the existence of two chromosome inheritance modes, 2n + n and n + n, in the context of the intraspecific hybridization of S. spontaneum. Additionally, hybridization between different ploidy S. spontaneum was also accompanied by chromosomal translocations (A1, A2, A18, A18) and loss (A2, A33-1, AA-4, and C2) that further resulted in the complexity of the S. spontaneum genome. Together, these findings highlight diverse chromosome inheritance in S. spontaneum hybridization, and provide a theoretical foundation for the further utilization of S. spontaneum germplasm in sugarcane breeding.

RDNA is abundant in various organisms, typically expressed as conserved tandem repeats. It plays a crucial role in ribosome synthesis, gene transcription, and expression, and it affects the occurrence of diseases in both animals and plants, aging, protein synthesis, genomic stability, and genome evolution across a wide range of organisms. Among the different types of rDNA, 35S rDNA (also referred to as 45S rDNA) and 5S rDNA are particularly important in plant research. The use of 35S rDNA and 5S rDNA as probes has enabled the study of chromosomal composition, revealing species characteristics that are valuable for crop breeding, evolutionary biology, systematics, and other fields. This review focuses on the application of 35S rDNA and 5S rDNA and discusses research findings on sugarcane and its related germplasm that have been obtained through fluorescence in situ hybridization. This information has provided a foundation for understanding the genetic relationships, genetics, breeding, and evolutionary classification of sugarcane.

Sugarcane (Saccharum spp.) is a globally vital high-biomass sugar crop with a massive demand for potassium (K). Low-K⁺ stress severely restricts its yield and stress resistance. Plasma membrane intrinsic proteins (PIPs) play pivotal roles in transmembrane water transport and ion homeostasis; however, their evolutionary characteristics and molecular mechanisms underlying nutritional stress responses in the complex polyploid sugarcane remain poorly understood. In this study, genome-wide identification in the sugarcane cultivar XTT22 yielded 149 PIP gene family members (comprising 54 PIP1s and 95 PIP2s). Phylogenetic and chromosomal localization analyses demonstrated that the sugarcane PIP family underwent drastic paralogous expansion during evolution, with tandem duplication acting as the core driving force for the dramatic expansion of the PIP2 subfamily. Spatiotemporal expression profiling unveiled significant modular functional division among PIP genes, identifying a core co-expression group driving rapid early seedling elongation and a PIP2-specific expression cluster dedicated to the physiological homeostasis of mature stems. Notably, the core member ScPIP2-70 exhibited significant early-induced responses at both transcriptional and protein levels in roots under low-K⁺ stress. Functional complementation assays in the K⁺-uptake deficient yeast strain R5421 further confirmed that the heterologous expression of ScPIP2-70 effectively rescued the growth defects of yeast under low-K⁺ conditions, demonstrating its potential transmembrane K⁺ transport activity. This study not only comprehensively elucidates the evolutionary dynamics and spatiotemporal expression profiles of the sugarcane PIP gene family but also uncovers the novel pleiotropic function of ScPIP2-70 in mediating low-K⁺ stress tolerance, providing critical theoretical support and candidate gene resources for breeding “potassium-efficient” sugarcane cultivars via modern biotechnology.

Hybridization between sugarcane (Saccharum spp.) and its wild relative Erianthus rockii offers a promising route to broadening the narrow genetic base of modern cultivars, but the authenticity and chromosome inheritance patterns of such hybrids remain poorly understood. In this study, we combined molecular marker (tetra-primer ARMS-PCR) and cytogenetic (genomic in situ hybridization, GISH) approaches to verify hybridity and track chromosome transmission in 24 F₁ and 12 BC₁ progeny. The F₁ hybrids exhibited a strict n + n transmission pattern, receiving exactly 15 chromosomes from E. rockii. When F₁ plants were used as the male parent in backcrosses, no BC₁ seeds were obtained due to complete pollen sterility. Remarkably, when F₁ plants served as the female parent, all 12 BC₁ clones retained the entire set of 15 E. rockii chromosomes intact, following an unconventional 2n + n pattern. These findings reveal a strong parent-of-origin effect and, for the first time, demonstrate that the whole E. rockii chromosome complement can be stably transmitted into backcross progeny without loss or recombination. This opens a direct route for introgressing complete wild genomes into sugarcane breeding lines, preserving complex polygenic traits and guiding rational crossing strategies.