Colletotrichum falcatum influences sucrose accumulation in sugarcane stalks by modulating the expression of SPS, SPP, SuSy, and invertases

Colletotrichum falcatum is one of the devastating fungal pathogens of sugarcane, accountable for the red rot pandemic in India. Sucrose, being main assimilatory product of sugarcane, has been accredited for its crucial roles as signaling molecule, and association with biotic responses against pathogens. This is the first study to investigate the effect of C. falcatum infection on sucrose metabolism in stalk tissues of red rot resistant (BO91) and susceptible (CoJ64) cultivars of sugarcane. Our experiment included nanoLCMS/MS-based investigation of peptide abundance of the proteins implicated in sucrose metabolism, followed by qRT-PCR-based validation at gene level. The results indicated that C. falcatum promotes sucrose biosynthesis in CoJ64 cultivar by enhancing the abundance of SPS-1, 4, 12, 14, and SPP-1, 2, 3, 5. In case of invertases, implicated in sucrose degradation, contrasting results of peptide abundance were pragmatic between AIs and ANIs after C. falcatum infection. C. falcatum infection induced the abundance of AI proteins (SAI-1, 2, 3, 8, 9, 12, 14, CWI-2, VI-1), whereas the abundance of ANI proteins was reduced (ANI-1, 4, 6, 10, 11) in BO91 cultivar. Similarly, fungal infection also reduced the peptide abundance of ANIs (ANI-6, 10) in CoJ64 cultivar. Peptide abundance of SuSy proteins, involved in irreversible catalysis of sucrose, was also enhanced by fungal infection in both the cultivars of sugarcane. Results indicated that SuSy-1 and 4 in BO91 cultivar, and SuSy-1 and 6 in CoJ64 cultivar were significantly induced by C. falcatum infection. The results display a positive impact of C. falcatum infection on sucrose accumulation in the stalk tissues of sugarcane.