The trehalose-6-phosphate synthase (TPS) gene family plays important roles in conferring plant stress resistance, but a comprehensive analysis of the gene family is lacking for sugarcane (Saccharum spp. hybrids). The objective of this study is to document functional classification, evolutionary characterization, and expression profiling of sugarcane TPS gene (ScTPS) family. Nine putative ScTPS genes were identified and assigned to two distinct classes based on gene structure and phylogeny. Phylogenetic analysis showed that 31 TPS genes from Arabidopsis, rice and sugarcane could be divided into five distinct clades, suggesting that there were at least five orthologous groups in monocot and dicot plants. Evolution analysis of TPS genes revealed that TPS family members appeared to have undergone strong negative selection. The strength of the selective pressure differed in most clades, especially Class I TPS genes, experienced significantly stronger negative selection pressure than Class II TPS genes. There were also cis-regulatory elements related to phytohormones and abiotic stresses. Additionally, ScTPS genes were found to exhibit divergent expression in response to simulated drought, salinity, and ABA stresses. Since ScTPS genes function in sugarcane adaptation to environmental stimuli, it might be used as a molecular marker in screening sugarcane germplasm for increased stress resistance.

TGA transcription factor (TF) family genes play a major role in the regulation of plant growth and development as well as in the defense against pathogen attack. Little is known about the TGA family genes and their functions in sugarcane. Here, a total of 16 TGA members were identified in the sugarcane genome by bioinformatic approaches. All members exhibited similar conserved motifs and contained a bZIP domain and a DOG1 domain, except for ShTGA15/16. Phylogenetic analysis demonstrated that 16 ShTGA family genes could be divided into eight clades, and evolved differently from Arabidopsis TGAs. All ShTGA family genes suffered a purifying selection during evolution. A wide range of cis-regulatory elements were found in the promoter of ShTGA genes including hormone regulatory elements, adversity response elements, light responsive elements, and growth and development regulatory elements. Most ShTGA expressions were increased in bud growth and developmental processes except for ShTGA10/11. It is worth noting that the expression of ShTGA13 was decreased after sugarcane was infected with Sporisorium scitamineum, and it was highly expressed in the resistant variety compared to the susceptible variety. Adding IAA, GA₃ and SA restored the expression of ShTGA13, suggesting an association with plant hormone regulatory pathways. Our study provides a framework for further functional studies of important ShTGA genes in development and stress response, and uncovered a previously unrecognized role of ShTGA13 in regulating resistance against S. scitamineum.

Sugarcane is a complex polyploid aneuploid cash crop, and transgenic varieties are important for molecular genetic and traditional breeding approaches. Herein, the sugarcane variety ROC22 served as the receptor, the Bar gene served as a screening marker, and positive and negative fragments of the ScD27.2 gene, upstream of strigolactones (SLs) biosynthesis genes driven by the 35S promoter, were introduced by Agrobacterium tumefaciens-mediated transformation. Regenerated plants were obtained by co-culture, screening culture, and differentiation induction, and 27 sense and antisense ScD27.2 transgenic seedlings were obtained by herbicide screening. PCR detection and 1% Basta (Glufosinate) application on leaves revealed Bar in all lines, with all testing positive for herbicide application and 23 containing the target gene (positive resistance screening rate = 87.5%). q-PCR and phenotypic analyses showed that ScD27.2 expression, plant height, tiller number, root length, stem diameter, and fresh weight were decreased in transgenic (ScD27.2R-9) compared with non-transgenic (NT and ScD27.2F-2) lines. ScD27.2 expression was downregulated, and growth potential was inhibited. Under 20% PEG treatment, malondialdehyde (MDA) content in ScD27.2R-9 was higher than in NT, while proline content was lower. Under drought stress, ScD27.2 expression, MDA levels, and proline content in ScD27.2F-2 and NT were higher than in non-treated controls, ScD27.2 expression increased with time, and MDA and proline levels also increased. ScD27.2 expression in ScD27.2R-9 decreased under 20% PEG treatment, MDA and proline increased (but not to NT levels), and growth was lower than NT. The 20% PEG treatment also increased the levels of (±)-2′-epi-5-deoxystrigol and (+)-abscisic acid in the rooting culture media of ScD27.2F-2, ScD27.2R-9, and NT lines, but the levels of (+)-abscisic acid content in ScD27.2R-9 was lower than in NT. Thus, interfering with ScD27.2 expression decreased resistance to 20% PEG treatment. ScD27.2 encodes a β-carotene isomerase involved in SLs biosynthesis that might function in sugarcane resistance to drought stress. It explains the role of SLs in sugarcane growth and development and responses to drought stress.

UV exposure is harmful to plants. Increasing resistance against UV light is thus of great importance to their growth. Para-Aminobenzoic acid (PABA) has major roles in many biological processes, involving nucleotide biosynthesis, DNA repair, and DNA methylation, which contributed to UV irradiation. However, no study reports the effect of PABA on UV tolerance, or details of the underlying molecular mechanisms are explored. Hence, the objective of the research is to study the protective effect of PABA on UV in Arabidopsis and explored the molecular mechanisms. We overexpressed PABA synthase gene (Pabs) from Mushroom Agaricus bisporus in Arabidopsis and observed reduced root growth and UV-C hyposensitivity exposed to 2500 J m⁻² UV-C light. UV-C-induced DNA damage was significantly reduced and the expression of decreased DNA methylation 1 (DDM1) was remarkably higher in the Pabs lines, suggesting that overexpression of Pabs may protect against UV-induced DNA damage. In addition, overexpression of Pabs leads to an elevated reactive oxygen species production at root tips and enhanced catalase and superoxide dismutase activity, which may correlate with the enhanced UV tolerance of the Pabs overexpression lines. In summary, overexpression of Pabs from A. bisporus enhances UV-C tolerance of Arabidopsis, suggesting that Pabs takes an important part in defence against DNA damage.

Sugarcane smut, caused by the fungus Sporisorium scitamineum, is the most challenging disease of sugarcane, causing significant losses in cane yield. There is a dearth of information on smut resistance mechanism in elite parents for the development of smut-resistant varieties. In the present study, we adopted joint Illumina- and Single Molecule Real-Time (SMRT)-based RNA-seq analysis to identify transcript expression in an smut-resistant and -susceptible parents (ROC25 and ROC22) infected with S. scitamineum. A total of 79,885 high-quality transcripts was obtained, including 60,115 open reading frames, 3692 alternate splicing isoforms, 1799 long non-coding RNAs, 29,139 simple sequence repeats, and 7794 transcription factors. About 92.72% of the total transcripts were annotated, which should have increased the available data amount for transcriptome profile analysis. There were 2033 and 9716 differentially expressed transcripts (DETs) in ROC22 and ROC25, respectively. The analyses of GO and KEGG enrichment showed that more GO terms and KEGG pathways were observed in ROC25 than ROC22. It was found that MAPK signalling pathway-plant, phenylpropanoid biosynthesis, plant-pathogen interaction, linoleic acid metabolism, and starch and sucrose metabolism were enriched both in resistant and susceptible parents. In addition, MAPK superfamily genes were differentially regulated in different parents, more DETs of MEKK1 and MKK4 were detected in resistant parent, and the relative expression levels of MKK5, MPK10, and MPK12 genes were specifically altered in resistant parent. It suggested that MAPK superfamily genes might play the important roles in the regulation of sugarcane response to S. scitamineum infection. Moreover, lots of transcription factors (TFs) associated with plant disease resistance were found to respond to S. scitamineum infection in both ROC22 and ROC25 parents, including WRKY, MYB, NAC, and AP2/ERF-ERF. Majority of the TFs were up-regulated. Compared to the susceptible ROC22 parent, the number of activated transcription factors in the resistant ROC25 parent was higher, indicating that these extra TFs might have positive effects in the defense against S. scitamineum. This study provides a comprehensive set of reference transcripts for sugarcane and thus increases our understanding on the interactions between sugarcane and S. scitamineum, which should be helpful in guiding on exploitation and utilization of smut-resistance gene resources.