A xylan glucuronosyltransferase gene exhibits pleiotropic effects on cellular composition and leaf development in rice

Abstract

Leaf chlorophyll content is an important physiological indicator of plant growth, metabolism and nutritional status, and it is highly correlated with leaf nitrogen content and photosynthesis. in this study, we report the cloning and identification of a xylan glucuronosyltransferase gene (OsGUX1) that affects relative chlorophyll content in rice leaf. Using a set of chromosomal segment substitution lines derived from a cross of wild rice accession ACC10 and indica variety Zhenshan 97 (ZS97), we identified numerous quantitative trait loci for relative chlorophyll content. one major locus of them for relative chlorophyll content was mapped to a 10.3-kb region that contains OsGUX1. the allele OsGUX1 AC from ACC10 significantly decreases nitrogen content and chlorophyll content of leaf compared with OsGUX1 ZS from ZS97. The overexpression of OsGUX1 reduced chlorophyll content, and the suppression of this gene increased chlorophyll content of rice leaf. OsGUX1 is located in Golgi apparatus, and highly expressed in seedling leaf and the tissues in which primary cell wall synthesis occurring. our experimental data indicate that OsGUX1 is responsible for addition of glucuronic acid residues onto xylan and participates in accumulation of cellulose and hemicellulose in the cell wall deposition, thus thickening the primary cell wall of mesophyll cells, which might lead to reduced chlorophyll content in rice leaf. These findings provide insights into the association of cell wall components with leaf nitrogen content in rice.Rice (Oryza sativa. L) providing a staple food for more than half of the population in the world, is a monocot model species for genetics, biology and functional genomics studies. Leaf photosynthesis has great potential for the improvement of rice yield, which will significantly contribute to addressing food demand challenge. The chloroplast of green tissue or leaf, as the most important supporter of carbon fixation and energy transformation, plays important roles in photosynthesis 1-3 . Both genetic and environmental factors have effect on the biochemical composition in chloroplast, thus affecting photosynthetic rate 4 .Previous studies have indicated that leaf color is a sensitive indicator of crop growth, metabolism and nutritional status, and it is closely related to the content of photosynthetic pigment, and positively correlated with leaf nitrogen (N) content 5-7 . Understanding the genetic and physiological bases of leaf nitrogen status is essential for efficient crop production and nitrogen management in intensive rice cropping systems. Leaf greenness is determined by specific properties, such as leaf chlorophyll content and chloroplast development, and leaf morphological characteristics (leaf thickness, surface structure and wall components). To study the genetic and molecular basis of leaf color, more than one hundred of rice mutants associated with leaf colors and chlorophyll content have been identified (http://archive.gramene.org/db/genes/). Several genes have been implicated in the chlorophyl...

Silencing ScGUX2 reduces xylan glucuronidation and improves biomass saccharification in sugarcane

“…The estimated degree of xylan glucuronidation ranged from 0.4% to 3.9% in transgenic lines, some of which are much lower than the levels observed in WT and EV controls, where approximately 4% and 3.5% of xyloses, respectively, had the GlcA branch. In another Poaceae species ( Oryza sativa ), OsGUX1 is also able to modulate the GlcA content when overexpressed or silenced (Gao et al ., 2020), as observed in our transgenic sugarcane lines.…”

“…The estimated degree of xylan glucuronidation ranged from 0.4% to 3.9% in transgenic lines, some of which are much lower than the levels observed in WT and EV controls, where approximately 4% and 3.5% of xyloses, respectively, had the GlcA branch. In another Poaceae species (Oryza sativa), OsGUX1 is also able to modulate the GlcA content when overexpressed or silenced (Gao et al, 2020), as observed in our transgenic sugarcane lines. The silencing of ScGUX2 expression and the concomitant decrease in the degree of xylan glucuronidation resulted in reduction of the plant cell wall recalcitrance, particularly seen in the increase in xylose released in the saccharification assay.…”

“…In Eucalyptus , EgrGUX1 and EgrGUX2 were identified in silico supporting studies for biomass quality in woody crop plants (Wierzbicki et al ., 2019). In the grass rice, OsGUX1 is also involved in xylan substitution, but it was reported that mutants surprisingly present a set of pleiotropic phenotypes ranging from reduced primary cell wall thickness and soluble sugar content to alterations in the chlorophyll and nitrogen contents (Gao et al ., 2020). It is important to study further the role of GUX genes and glucuronidation of xylan in grasses.…”

Deciphering the Genetic Basis of Lodging Resistance in Wild Rice Oryza longistaminata

“…Two genes draw our attention according to their gene annotation. First is MH01t0727100-1 encoding a UDPglucuronate:xylan alpha-glucuronosyltransferase 1, which can enhance mechanical strength of the stem (Gao et al, 2020). Epigenetic plays an increasing important role for plant breeding and selection of adaptive traits.…”

Candidate Genes and Pathways in Rice Co-Responding to Drought and Salt Identified by gcHap Network

“…These genes are helpful to study rice leaf traits under drought stress. GHd2 regulates leaf senescence under drought stress by interacting with different proteins; OsHB4 overexpression can alter leaf morphology and reduce water loss; Gao et al (2020) found that OsGUX1 affects relative chlorophyll content in rice leaves [ 27 , 28 , 29 ]. At the same time, drought-tolerant rice varieties, such as Indian local varieties Kalajeera, Machakanta and Haladichudi, can also be distinguished by leaf traits [ 30 , 31 , 32 ].…”