Identification of Functional Brassinosteroid Receptor Genes in Oaks and Functional Analysis of QmBRI1

Brassinosteroids (BRs) play important regulatory roles in plant growth and development, with functional BR receptors being crucial for BR recognition or signaling. Although functional BR receptors have been extensively studied in herbaceous plants, they remain largely under-studied in forest tree species. In this study, nine BR receptors were identified in three representative oak species, of which BRI1s and BRL1s were functional BR receptors. Dispersed duplications were a driving force for oak BR receptor expansion, among which the Brassinosteroid-Insensitive-1 (BRI1)-type genes diverged evolutionarily from most rosids. In oak BRI1s, we identified that methionine in the conserved Asn-Gly-Ser-Met (NGSM) motif was replaced by isoleucine and that the amino acid mutation occurred after the divergence of Quercus and Fagus. Compared with QmBRL1, QmBRI1 was relatively highly expressed during BR-induced xylem differentiation and in young leaves, shoots, and the phloem and xylem of young stems of Quercus mongolica. Based on Arabidopsis complementation experiments, we proved the important role of QmBRI1 in oak growth and development, especially in vascular patterning and xylem differentiation. These findings serve as an important supplement to the findings of the structural, functional and evolutionary studies on functional BR receptors in woody plants and provide the first example of natural mutation occurring in the conserved BR-binding region (NGSM motif) of angiosperm BRI1s.

The effect of climate change on the richness distribution pattern of oaks (Quercus L.) in China

Increased concentration of greenhouse gases in the air is acknowledged as one of the main reason for observed global climatic change. This phenomenon significantly affects the species geographical distribution, and changes their richness distribution pattern. Oak (Quercus L.) is an important component of forests in China, and it has significant ecological value. Based on the distribution data of 35 species and 19 bioclimatic variables, the potential richness distribution of Quercus L. in China was predicted using the MaxEnt model under present climatic conditions and three different emission scenarios in the years 2050 and 2070 with six General Circulation Models (GCMs). The results revealed that Quercus L. at present was primarily distributed in the mountainous areas of southwestern China. The simulations indicated that climate change could affect the spatial pattern of the richness distribution, and if climate change intensified, its impact would gradually increase. As temperatures rise, the distribution of Quercus L. was predicted to be concentrated, and suitable areas of certain species would contract. These species may migrate to high altitudes or high latitudes. The high percentage of species lost is the reason for the higher turnover values in the mountainous areas, while other regions are mostly be influenced by the high percentage of species gained associated with the northward shift of species. Predicting changes in the richness distribution pattern of Quercus L. as a result of climate change can help us understand the biogeography of Quercus L. and enact conservation strategies to minimize the impacts of climate change.