Transcriptional Changes of Cell Wall Organization Genes and Soluble Carbohydrate Alteration during Leaf Blade Development of Rice Seedlings.

Jae-Yeon Joo,Jwakyung Sung,Me-Sun Kim

doi:10.3390/plants10050823

Abstract

Plant cell walls have two constituent parts with different components and developmental stages. Much of the mystery concerning the mechanisms of synthesis, decomposition, modification, and so forth, has been resolved using omics and microscopic techniques. However, it still remains to be determined how cell wall development progresses over time after leaf emergence. Our focus in the present study was to expand our knowledge of the molecular mechanisms associated with cell wall synthesis in rice leaf blade during three distinct stages (sink, sink-to-source transition, and source). The RNA-seq, quantitative reverse transcription PCR (qRT-PCR) and carbohydrate concentrations were evaluated using developing fifth leaf blades harvested at different time points. The results revealed that some of the essential genes for the primary cell wall (PCW) were highly upregulated in the sink-to-source transition compared to the sink stage, whereas those essential to the secondary cell wall (SCW) displayed relatively higher levels (p < 0.05) during the source stage. The concentrations of soluble carbohydrates differed via type rather than stage; we observed higher monosaccharides during the sink stage and higher di- and oligo-saccharides during the sink-to-source transition and source stages. In conclusion, our findings suggest that the transcriptional regulation of plant cell wall biosynthesis genes are both synchronistic with and independent of, and directly and indirectly governed by, the abundance of soluble carbohydrates in the developing leaf blade, and, finally, raffinose is likely to play a transport role comparable to sucrose.

Highlights

The cell walls (CWs) are characterized into two types, primary and secondary
We have investigated cell wall organization according to the transcriptomes present during rice leaf blade development
By comparing differentially expressed genes (DEGs) and identifying highly expressed genes during blade maturation (Figure 2), we found that the type of increased genes was strongly dependent on the maturity of the blades (Figure 3)

Summary

Introduction

The cell walls (CWs) are characterized into two types, primary and secondary. The formation of each CW is clearly distinguished by composition, developmental stage and function. CWs are usually affected in composition, thickness and strength through physicochemical and biological reactions during leaf development These developmental processes are well regulated through a variety of functionally specialized enzymes, such as glycosyltransferases (i.e., cellulose-synthase-like, CslC), xyloglucan endotransglucosylase/hydrolase (XTH), glycosyltransferase (GT) and acyltransferase (AT). The growth of new leaves absolutely depends on the import of assimilates synthesized in older ones The sink tissues, such as young leaves and roots, continuously receive photosynthetic products, mainly in the form of sucrose, until they can support themselves. The concentrations of soluble carbohydrates in developing leaves differs with regard to the type of sugar, with increases in sucrose (disaccharide) being leaf aging-dependent and the highest levels of glucose, fructose, and galactose (monosaccharide) found in the elongation stage [10]

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