Expression analysis of genes associated with sucrose accumulation and its effect on source–sink relationship in high sucrose accumulating early maturing sugarcane variety

Abstract

Sucrose synthesis/accumulation in sugarcane depends on the source-sink communication wherein source responds to sink demand for photoassimilate supply. Sucrose in stalk (sink) acts as signal, and sends feedback to restrain further synthesis of sucrose by regulating photosynthetic efficiency of leaves (source). Hence sucrose synthesis/accumulation is controlled by many genes and regulatory sequences including 3 invertases (SAI, CWI, NI), sucrose synthase (SuSy) and sucrose phosphate synthase (SPS). SPS and invertase play key role in enhancing sink strength which ultimately promotes greater sucrose accumulation in the sink tissues. In present study, a significant positive correlation was found between sucrose% of source and sink tissues which was greater in the top (R 2 = 0.679) than middle (R 2 = 0.580) and bottom (R 2 = 0.518) internodes, depicting that sucrose accumulation in the stalk bears a direct relation with sucrose translocation efficiency from source. Results indicated an increased sucrose% with maturity, while reducing sugar content decreased with crop growth. qRT-PCR results exhibited an elevated expression of invertase in immature sink tissues depicting increased sink requirement, which declined with maturity. Similarly, increased PEP carboxylase gene expression as observed supported the fact that higher sink demand results in enhanced photosynthetic rate and thus influences the source activity. SPS was found active at initial stage of cane development indicating its role in sucrose synthesis. Thus by studying expression patterns of the different genes both, in source and sink tissues, a better understanding of the sucrose accumulation pathway in sugarcane is possible, which in turn can help in elucidating ways to enhance sucrose concentration in sink.

Differential expression in leaves of Saccharum genotypes contrasting in biomass production provides evidence of genes involved in carbon partitioning

“…As a C4 grass, sugarcane photosynthesis includes a pathway to obtain a four-carbon compound, a process that occurs in the mesophyll and is orchestrated by PEPC. In agreement with Verma and colleagues [40], we noted that high biomass genotypes may require a more intense expression of PEPC coding genes to support metabolic functions other than sucrose accumulation. Expression of PEPC genes was lower in young leaves associated with maturing culms but was practically invariable in leaves connected with more mature stalks [40].…”

“…In agreement with Verma and colleagues [40], we noted that high biomass genotypes may require a more intense expression of PEPC coding genes to support metabolic functions other than sucrose accumulation. Expression of PEPC genes was lower in young leaves associated with maturing culms but was practically invariable in leaves connected with more mature stalks [40]. In addition, a group of photophosphorylation genes coding for Psa, Psb and cytochrome proteins formed a downregulated cluster in low biomass genotypes (Figure 12 in Additional file 3).…”

Differential Expression in Leaves of Saccharum Genotypes Contrasting in Biomass Production Provides Evidence of Genes Involved in Carbon Partitioning

“…However, CWINV overexpression can promote monomer accumulation in leaves, impairing carbohydrate storage and affecting growth, as described in cassava (42). SPS and CWINV have been shown to be highly expressed in sugarcane before maturation of culms, precisely to allow the development of leaves and to compensate for sucrose storage requirements in sink tissue (40). These authors also pointed out that genes coding for enzymes such as PEPC and SUT1 can show stable or increased expression levels in more mature leaves.…”

“…In agreement with Verma and colleagues (40), we noted that high biomass genotypes may require a more intense expression of PEPC coding genes to support metabolic functions other than sucrose accumulation. Expression of PEPC genes was lower in young leaves associated with maturing culms but was practically invariable in leaves connected with more mature stalks (40). In addition, a group of photophosphorylation genes coding for Psa, Psb and cytochrome proteins formed a downregulated cluster in low biomass genotypes (Figure 12 in Additional le 3).…”

Effect of GA3 and Gly Plant Growth Regulators on Productivity and Sugar Content of Sugarcane

“…As a result, the application of GA3 showed a positive impact on some stages of development leading to an increase in cane yield compared to untreated controls. Various research programs revealed that GA3 had an effect on the activity of sucrose phosphosynthase, one of the major enzymes involved in the synthesis of sucrose [7], and promoted the proliferation of sink tissues, leading to an improved assimilation process in sugarcane [8][9][10]; economic efficiency was thereby enhanced. In addition, GA3 increased abiotic stress tolerance in crops like sugarcane that are grown in, for example, salinated environments [11].…”