Genomic landscape of a relict fir-associated fungus reveals rapid convergent adaptation towards endophytism

Changes of endophytic microbial community in Rhododendron simsii roots under heat stress and its correlation with leaf physiological indicators

Introduction

The response mechanism of Rhododendron simsii and its endophytic microorganism to heat stress is still unclear.

Methods

The light incubator was used to set the temperature gradients, and the control (CK) was (day/night: 14/10 h) 25/22°C, the moderate-heat-stress (MHS) was 35/30°C and the high-heat-stress (HHS) was 40/35°C.

Results

Compared with CK, MHS significantly increased the contents of malondialdehyde, hydrogen peroxide, proline, and soluble sugar, as well as the activities of catalase and peroxidase in leaf, while HHS increased the activities of ascorbate peroxidase, and decreased chlorophyll content. Compared with CK, MHS reduced soil available nitrogen (N) content. Both heat stress changed the endophytic microbial community structure in roots. MHS enriched Pezicula and Paracoccus, while HHS significantly enriched Acidothermus and Haliangium. The abundance of Pezicula positively correlated with the contents of chlorophyll a and proline in leaf, and negatively correlated with soil ammonium N content. The abundance of Pezicula and Haliangium positively correlated with soluble sugar and malondialdehyde contents, respectively.

Conclusions

Our results suggest that root endophytic microorganisms play an important role in helping Rhododendron resisting heat stress, mainly by regulating soil N content and plant physiological characteristics.

Additions to the Knowledge of the Genus Pezicula (Dermateaceae, Helotiales, Ascomycota) in China

Simple Summary

Species of the genus Pezicula are endophytes, phytopathogens, or saprobes, and some of them have biocontrol potential, promoting plant growth and resistance to environmental stress. The species diversity of Pezicula in China was reviewed. Two new species (P. ellipsoids and P. fusispora) and two new Chinese records (P. acericola and P. carpinea) were discovered using morphological and molecular approaches. Descriptions and illustrations of macroscopic and microscopic features were provided for the new and newly found taxa. Pezicula aurantiaca was excluded from the fungal catalogue of China. Together with the previously reported taxa (P. cinnamomea, P. ericae, P. heterochroma, P. magnispora, P. melanigena, P. neosporulosa, P. ocellata, P. rhizophila, P. cf. rubi, and P. subcarnea), 14 Pezicula species are currently known from China. The results provide updated information and improve our understanding of the genus.

Abstract

We describe two new species of Pezicula (Dermateaceae, Ascomycota), P. ellipsoides and P. fusispora, which are discovered in China. Pezicula ellipsoides sp. nov. is distinct in producing 2–3 stipitate apothecia on a basal stroma with a light yellow hymenium, broadly ellipsoid 0–1(–2)-septate ascospores, and divergent DNA sequence data. Pezicula fusispora sp. nov. is characterized by sessile apothecia, 0.3–0.8 mm in diam, a yellowish hymenium, J+ asci 135–170 × 15–21 μm, multiseptate ascospores, 33–48 × 7–10.3 μm, and growing on rotten bamboo. In addition, Pezicula acericola and P. carpinea are reported for the first time from China, and 11 Pezicula species previously reported from China are reviewed and briefly noted, of which one was a misidentified species. Phylogenetic analyses inferred from ITS nrDNA sequences confirm the placement of P. ellipsoides and P. cinnamomea in the genus Pezicula.