Sucrose is the primary form of mobile photoassimilates, and its level is regulated by sucrose-phosphate synthase (SPS) in plants. Increasing in the SPS activity was accompanied by an increase in sucrose accumulation. This study was designed to examine the effect of the overexpression sugarcane SoSPS1 gene on sucrose metabolizing enzymes, growth, and grain yield of indica rice. The SoSPS1 gene was constructed in a binary vector under the control of a rice ubiquitin promoter and transformed into indica rice using an Agrobacterium vector. Five lines of transgenic rice were selected to develop homozygous transgenic lines and used for analysis. The overexpression of the SoSPS1 gene significantly increased the transcript and protein levels, followed by increasing in SPS activity and sucrose content in the leaves of the transgenic rice lines. Moreover, the activity of soluble acid invertase (SAI) was elevated rather than sucrose synthase (SuSy) in the transgenic lines. The increase in the sucrose-degrading enzymes leads to an increase in plant growth and development. The plant height and number of tillers were significantly higher in the transgenic line compared to non-transgenic (NT) rice. In addition, the amylose content, the number of seeds per panicle, and the weight of 1000 grains of seed, including dry biomass weight, were increased in the transgenic lines. The results indicated that enhancement of SPS activity, as well as sucrose content, provides a higher carbon partitioning for higher growth and productivity of the transgenic rice lines.

Sugarcane mosaic virus (SCMV), sugarcane streak mosaic virus (SCSMV), and sorghum mosaic virus (SrMV) are the causative pathogens of mosaic disease. This study aimed to identify mosaic virus infection and its impact on photosynthetic and antioxidant gene expression in eight commercial sugarcane cultivars grown on sugarcane plantations in East Java, Indonesia. The disease incidence and severity were observed in symptomatic leave samples, and then the virus was identified. A high incidence and severity of mosaic symptoms were observed in the PS881 and NX04 cultivars compared with the other cultivars. RT-PCR analysis detected SCSMV infection in all cultivars; double infections with SCSMV and SCMV in the PS881, PS882, and Cening cultivars; and triple infections with SCSMV, SCMV, and SrMV in the PS881 cultivar. Ascorbate peroxidase (Apx) expression was upregulated in all virus-infected cultivars and significantly increased in the triple-infected PS881 cultivar. However, catalase (Cat) expression was only slightly increased in the PS881 cultivar. The chlorophyll content was reduced, and the PsaA gene was downregulated in all cultivars. The expression of PsaA, RbcS, and Sps was significantly suppressed in the triple-infected PS881 cultivar. Moreover, the downregulation of both the RbcS and Pepc genes was concomitant with that of their protein levels.

Sugarcane is considered as an industrial crop that produces sugar. The number of transgenic sugarcane on the market is currently increasing. Therefore, investigation of the potential allergens and toxics in transgenic sugarcane is necessary, since there is less information regarding food safety for human consumption. Bioinformatics and experimental analysis were used for the validation of the allergenic potential of transgenic sugarcane overexpressing sucrose–phosphate synthase (SPS). Bioinformatics analysis showed that SPS has no homology with any known allergenic proteins. However, eight-residues identical contiguous sequence was detected, and further specific assessment is required to confirm the potential of allergenicity. The results of protein stability evaluation showed that SPS gradually decreased at 28 °C and rapidly inactivated at 60 °C and 90 °C by heat treatment. In addition, total protein was degraded by simulated gastric fluids (SGF), and simulated intestine fluid (SIF) assays for one-minute incubation. The level of specific IgE in the transgenic sugarcane and controls also showed no potential risk of allergy. An acute oral toxicity assay was performed by oral gavage of transgenic sugarcane juice in mice. The LD₅₀ for transgenic sugarcane juice was >25 gr/kg body weight. We propose a development method for allergenicity and toxicity assessment in transgenic sugarcane.

Water deficit is one of the most critical factors for determining the growth and yield of sugarcane. Understanding the physiological and molecular mechanisms of sugarcane responses is essential for developing resilient cultivars. In this study, three sugarcane cultivars, NX04 (sensitive), BL (moderate), and NXI-4T (tolerant), were grown in a greenhouse for 2 months and then subjected to drought stress for 8 days after planting. Morphological variation showed that the tolerant sugarcane cultivar exhibits a longer root system and delays leaf chlorosis and rolling. Malondialdehyde (MDA) content was increased in the sensitive and moderate cultivars, although it slightly increased in the tolerant cultivars at 8 days after drought stress. The increase was accompanied by increases in proline content and in gene expression of the catalase (Cat) and ascorbate peroxidase (Apx) across all cultivars, which protect cells from oxidative damage. Interestingly, the expression of the photosynthetic Pepc (phosphoenolpyruvate carboxylase) and Sps (sucrose-phosphate synthase) genes was significantly decreased, whereas SPS activity increased under drought stress. This implies that the SPS protein may be regulated through post-translational modification. The expression of transcription factors (TFs) of NAC, rather than DREB, was significantly upregulated in the tolerant cultivar under 8 days of drought stress, in line with the delay of chlorosis.

Sugarcane streak mosaic virus (SCSMV) is one of the mosaic viruses found in mixed infection with two or more viruses. Infections of mosaic viruses show highly similar mosaic symptoms and are difficult to distinguish. This study aimed to develop a specific antibody against SCSMV that could potentially be utilized to differentiate mosaic virus infections. The cDNA encoding the coat protein (CP) of SCSMV was isolated by RT-PCR from the symptomatic sugarcane leaves. The cDNA was then used for the production of CP for the development of its polyclonal antibody. The nucleotide sequence of the cDNA showed high homology of 94.2–97.3% at the amino acid level with the CP-cDNA of SCSMV isolated from India (AM749403.1), Africa (OR195142.1), and USA (U75456.1). CP was produced as a recombinant protein with a molecular size of 36.5 kDa in Escherichia coli. The injection of recombinant CP into a rabbit resulted in the production of polyclonal antibodies, which were used for the immunodetection of SCSMV in sugarcane. Immunoblot analysis revealed a specific reaction of SCSMV-CP in symptomatic sugarcane leaves. ELISA (Enzyme-Linked Immunosorbent Assay) and IC-RT-PCR (Immunocapture-Reverse Transcription-Polymerase Chain Reaction) using the CP antibody proved successful for detecting SCSMV infection in sugarcane leaves. The results indicate that the SCSMV-CP antibody is suitable for an immunodetection system and exhibits high specificity for SCSMV infection.