Analysis of variance of the mealybug colony growth rate with ant tending and parasitic pressure.

<p>Analysis of variance of the mealybug colony growth rate with ant tending and parasitic pressure.</p

Analysis of variance of the percentage parasitism with ant tending and parasitic pressure.

<p>Analysis of variance of the percentage parasitism with ant tending and parasitic pressure.</p

Relationship between mealybug colony growth and level of ant tending.

<p>(A): Initial mealybug density and growth rate of the mealybugs; (B): Level of ant tending and growth rate of mealybugs.</p

Density-Dependent Benefits in Ant-Hemipteran Mutualism? The Case of the Ghost Ant <i>Tapinoma melanocephalum</i> (Hymenoptera: Formicidae) and the Invasive Mealybug <i>Phenacoccus solenopsis</i> (Hemiptera: Pseudococcidae)

<div><p>Although density-dependent benefits to hemipterans from ant tending have been measured many times, few studies have focused on integrated effects such as interactions between ant tending, natural enemy density, and hemipteran density. In this study, we tested whether the invasive mealybug <i>Phenacoccus solenopsis</i> is affected by tending by ghost ants (<i>Tapinoma melanocephalum</i>), the presence of parasitoids, mealybug density, parasitoid density and interactions among these factors. Our results showed that mealybug colony growth rate and percentage parasitism were significantly affected by ant tending, parasitoid presence, and initial mealybug density separately. However, there were no interactions among the independent factors. There were also no significant interactions between ant tending and parasitoid density on either mealybug colony growth rate or percentage parasitism. Mealybug colony growth rate showed a negative linear relationship with initial mealybug density but a positive linear relationship with the level of ant tending. These results suggest that benefits to mealybugs are density-independent and are affected by ant tending level.</p></div

Effect of ant tending, the presence of parasitoids, and initial mealybug density on mealybug colony growth.

<p>(A): Ant tending; (B): Parasitoid; (C): Initial mealybug density.</p

Effect of ant tending and parasitoid density on the percentage of parasitism.

<p>(A): Ant tending; (B): Parasitoid density.</p

Analysis of variance of the percentage parasitism with ant tending and initial mealybug density.

<p>Analysis of variance of the percentage parasitism with ant tending and initial mealybug density.</p

Effect of ant tending, the presence of parasitoids, and initial mealybug density on the percentage of parasitism.

<p>(A): Ant tending; (B): Initial mealybug density.</p

Role of UDP-Glucuronic Acid Decarboxylase in Xylan Biosynthesis in Arabidopsis

UDP-xylose (UDP-Xyl) is the Xyl donor used in the synthesis of major plant cell-wall polysaccharides such as xylan (as a backbone-chain monosaccharide) and xyloglucan (as a branching monosaccharide). The biosynthesis of UDP-Xyl from UDP-glucuronic acid (UDP-GlcA) is irreversibly catalyzed by UDPglucuronic acid decarboxylase (UXS). Until now, little has been known about the physiological roles of UXS in plants. Here, we report that AtUXS1, AtUXS2, and AtUXS4 are located in the Golgi apparatus whereas AtUXS3, AtUXS5, and AtUXS6 are located in the cytosol. Although all six single AtUXS T-DNA mutants and the uxs1 usx2 uxs4 triple mutant show no obvious phenotype, the uxs3 uxs5 uxs6 triple mutant has an irregular xylem phenotype. Monosaccharide analysis showed that Xyl levels decreased in uxs3 uxs5 uxs6 and linkage analysis confirmed that the xylan content in uxs3 xus5 uxs6 declined, indicating that UDP-Xyl from cytosol AtUXS participates in xylan synthesis. Gel-permeation chromatography showed that the molecular weight of non-cellulosic polysaccharides in the triple mutants, mainly composed of xylans, is lower than that in the wild type, suggesting an effect on the elongation of the xylan backbone. Upon saccharification treatment stems of the uxs3 uxs5 uxs6 triple mutants released monosaccharides with a higher efficiency than those of the wild type. Taken together, our results indicate that the cytosol UXS plays a more important role than the Golgi-localized UXS in xylan biosynthesis