UDP-Glucose Pyrophosphorylase is Rate Limiting in Vegetative and Reproductive Phases in Arabidopsis thaliana

Abstract

UDP-glucose pyrophosphorylase (UGPase) is an important enzyme in the metabolism of UDP-glucose, a precursor for the synthesis of carbohydrate cell wall components, such as cellulose and callose. The Arabidopsis thaliana genome contains two putative genes encoding UGPase, AtUGP1 and AtUGP2. These genes are expressed in all organs. In order to determine the role of UGPase in vegetative and reproductive organs, we employed a reverse genetic approach using the T-DNA insertion mutants, atugp1 and atugp2. Despite a significant decrease in UGPase activity in both the atugp1 and atugp2 single mutants, no decrease in normal growth and reproduction was observed. In contrast, the atugp1/atugp2 double mutant displayed drastic growth defects and male sterility. At the reproductive phase, in the anthers of atugp1/atugp2, pollen mother cells developed normally, but callose deposition around microspores was absent. Genes coding for enzymes at the subsequent steps in the cellulose and callose synthesis pathway were also down-regulated in the double mutant. Taken together, these results demonstrate that the AtUGP1 and AtUGP2 genes are functionally redundant and UGPase activity is essential for both vegetative and reproductive phases in Arabidopsis. Importantly, male fertility was not restored in the double knockout mutant by an application of external sucrose, whereas vegetative growth was comparable in size with that of the wild type. In contrast, an application of external UDP-glucose recovered male fertility in the double mutant, suggesting that control of UGPase in carbohydrate metabolism is different in the vegetative phase as compared with the reproductive phase in A. thaliana.

Genome-Wide Association Mapping Reveals That Specific and Pleiotropic Regulatory Mechanisms Fine-Tune Central Metabolism and Growth in Arabidopsis

“…Seed set is known to be especially dependent on metabolism (Lauxmann et al, 2016), and this trait was previously reported to be impaired in the double ugp1 ugp2 mutant (Meng et al, 2009;Park et al, 2010). The ugp1, vac-inv, and apl1 KO lines displayed shorter and aborted siliques ( Figure 5A) and a significant increase in seed abortion (P < 0.05; Figure 5B) in longday conditions (16-h photoperiod) compared with wild-type plants.…”

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

“…There are at least nine clades of nucleotide sugar pyrophosphorylases ( Figure 1A), which have different activities and physiological functions (Kotake et al, 2010). UDP-Glc pyrophosphorylases generate UDP-Glc, the starting substrate of UDP-sugar metabolism, which is used for the synthesis of cellulose and b-1,3-glucan and for the b-1,4-glucan backbone of xyloglucan (Hayashi et al, 1987;Gordon and Maclachlan, 1989;Cocuron et al, 2007;Park et al, 2010). A plant-specific enzyme, UDP-sugar pyrophosphorylase (USP), converts various monosaccharide 1-Ps to their respective UDP-sugars in the salvage pathway and is required for pollen development (Kotake et al, 2004(Kotake et al, , 2007Schnurr et al, 2006).…”

Demonstration <i>in vivo</i> of the role of <i>Arabidopsis</i> PLIM2 actin-binding proteins during pollination

“…RT-PCR analysis Semiquantitative RT-PCR was performed according to Park et al (2010) with slight modifications. Briefly, mRNA was isolated from the tissues described in Plant Materials using a Fast Track 2.0 mRNA isolation kit (Invitrogen, San Diego, CA, USA).…”

“…Plant transformation Plant transformation was performed according to Park et al (2006) and Park et al (2010). Briefly, transgenic Arabidopsis plants were generated with the Agrobacterium binary vector by the floral dip method (Clough and Bent, 1998).…”