The carbon reactions of photosynthesis: role of lectins and glycoregulation

Abstract

Modulation of glycoregulation in agriculture is reviewed here with emphasis on the elucidation of previously unknown pathways involving vacuolar lectins as well as a bypass of lectins that direct free sugars toward productivity. The reversible binding sequences of the endogenous lectin cycle are compared to an induced lectin bypass, as follows. (1) In the cycle, carbohydrate ligands, with similar binding specificities that compete for binding sites on lectins, are involved in the natural cycle of sugar exchanges. (2) For the bypass, tightly bound ligands that occupy lectins prevent free sugars from binding, making them available for productivity. This bypass is induced by methyl-α-D-mannopyranoside, a biochemical plant growth regulator for photosynthesis. Integration of this novel technology, with structural elements crucial for ligand binding by the lectins and with nitrogen assimilation, provides the basis for successful modulation of glycoregulation in crops for enhancement of quality and quantity.

Functional Characterization of an Amaranth Natterin-4-Like-1 Gene in Arabidopsis thaliana

“…The negative effect on vegetative and reproductive growth caused by the overexpression of this gene in A. thaliana was also an unexpected outcome considering that is was contrary to published data describing lectin-induced mitosis in some root apical meristem tissues (Bonner, 2009) and to lectindependent modulation of sugar metabolism and/or signaling leading to increased plant productivity (Nonomura et al, 2020;Moradi et al, 2021). On the other hand, it was in agreement with a study in which detrimental effects on plant growth and development were reported in A. thaliana plants overexpressing a lectin receptor kinase used as a sensor for extracellular nicotinamide adenine dinucleotide and with the suppressed growth observed in A. cruentus hairy roots transformed with AhN4L-2, an homolog of AhN4L-1 (Castellanos-Arévalo, 2020).…”

Exploring the Developmental Progression of Endosperm Cavity Formation in Maize Grain and the Underlying Molecular Basis Using X-Ray Tomography and Genome Wide Association Study

“…Lectin family proteins possess at least one carbohydrate recognition domain (CRD), which enables reversible binding to carbohydrates. This is critical for maintaining sugar-related osmotic balance in the plant cell via endogenous lectin cycle, in which lectin binds to sugar to form a sugar-complex rendering them osmotically inert when sugar becomes surplus and release sugar for utilization when needed ( Nonomura et al, 2020 ). Zm00001d010919 encodes a protein kinase superfamily protein, Pto kinase interactor1 with unknown biological function, whereas Zm00001d007403 encodes a chalcone synthase (CHS), which functions in the synthesis of maysin in maize, which is a C-glycosyl flavone found in maize silk tissue that confers resistance to corn earworm ( Meyer et al, 2007 ).…”

Review: The multiple roles of plant lectins

“…Vacuolar lectins have been suggested to play a role in the carbon reactions of photosynthesis [50,51]. Sugars produced by the photosynthetic carbon reduction cycle are transported from the chloroplasts to the vacuole of the cell, where they can bind with lectins (Fig.…”

“…Since early research shows that plant lectins can also interact with hydrophobic ligands (e.g. porphyrins, phytohormones) [52,53], it was proposed that lectins can play a role as mediators for transfer of information, both by acting as translators of the glycocode and by interacting with plant growth regulators [26,51,54].…”