Molecular and Histologic Adaptation of Horned Gall Induced by the Aphid Schlechtendalia chinensis (Pemphigidae).

Qin Lu,Yongzhong Cui,Ming-Shun Chen,Nawaz Haider Bashir,Hang Chen,Zixiang Yang,Juan Liu,Xiaoming Chen,Shuxiao Shao

doi:10.3390/ijms22105166

Abstract

Chinese galls are the result of hyperplasia in host plants induced by aphids. The metabolism and gene expression of these galls are modified to accommodate the aphids. Here, we highlight the molecular and histologic features of horned galls according to transcriptome and anatomical structures. In primary pathways, genes were found to be unevenly shifted and selectively expressed in the galls and leaves near the galls (LNG). Pathways for amino acid synthesis and degradation were also unevenly shifted, favoring enhanced accumulation of essential amino acids in galls for aphids. Although galls enhanced the biosynthesis of glucose, which is directly available to aphids, glucose content in the gall tissues was lower due to the feeding of aphids. Pathways of gall growth were up-regulated to provide enough space for aphids. In addition, the horned gall has specialized branched schizogenous ducts and expanded xylem in the stalk, which provide a broader feeding surface for aphids and improve the efficiency of transportation and nutrient exchange. Notably, the gene expression in the LNG showed a similar pattern to that of the galls, but on a smaller scale. We suppose the aphids manipulate galls to their advantage, and galls lessen competition by functioning as a medium between the aphids and their host plants.

Highlights

Plant galls are outgrowths of various plant tissues after stimulation by organisms ranging from insects to bacteria
Horned galls were located on rachis wings of the plant R. chinensis and induced by the aphid S. chinensis (Figure 1a,b)
We found that genes which regulated the ‘starch and sucrose metabolism’ and ‘other glycan degradation’ were more highly expressed in the gall tissues, and β-glucosidase regulated the last step in the starch and sucrose metabolism pathway by hydrolyzing the cellobiose or β-D-glucoside into D-glucose

Summary

Introduction

Plant galls are outgrowths of various plant tissues after stimulation by organisms ranging from insects to bacteria. They are outcomes of the interaction between parasites and their host plants [1]. In contrast to normal tissues, parasites are able control the gall to suit the parasite’s needs. The gall is a sink of photosynthate that can accumulate and store nutrients, and provide the necessary nutrients for the growth and development of galling insects by intercepting organic matter and the accumulation of inorganic nutrients (i.e., nutrition hypothesis) [8]. The gall is a microenvironment that protects the inducers against inclement weather (i.e., microenvironment hypothesis) [9,10]

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