Genome-Wide Identification and Characterization of Warming-Related Genes in Brassica rapa ssp. pekinensis

The Arabidopsis Proteins AtNHR2A and AtNHR2B Are Multi-Functional Proteins Integrating Plant Immunity With Other Biological Processes

AtNHR2A (Arabidopsis thaliana nonhost resistance 2A) and AtNHR2B (Arabidopsis thaliana nonhost resistance 2B) are two proteins that participate in nonhost resistance, a broad-spectrum mechanism of plant immunity that protects plants against the majority of potential pathogens. AtNHR2A and AtNHR2B are localized to the cytoplasm, chloroplasts, and other subcellular compartments of unknown identity. The multiple localizations of AtNHR2A and AtNHR2B suggest that these two proteins are highly dynamic and versatile, likely participating in multiple biological processes. In spite of their importance, the specific functions of AtNHR2A and AtNHR2B have not been elucidated. Thus, to aid in the functional characterization of these two proteins and identify the biological processes in which these proteins operate, we used immunoprecipitation coupled with mass spectrometry (IP-MS) to identify proteins interacting with AtNHR2A and AtNHR2B and to generate their interactome network. Further validation of three of the identified proteins provided new insights into specific pathways and processes related to plant immunity where AtNHR2A and AtNHR2B participate. Moreover, the comprehensive analysis of the AtNHR2A- and AtNHR2B-interacting proteins using published empirical information revealed that the functions of AtNHR2A and AtNHR2B are not limited to plant immunity but encompass other biological processes.

High ambient temperature leads to reduced FT expression and delayed flowering in Brassica rapa via a mechanism associated with H2A.Z dynamics

Flowering time is a relevant agronomic trait because is crucial for the optimal formation of seeds and fruits. The genetic pathways controlling this developmental phase transition have been studied extensively in Arabidopsis thaliana. These pathways converge in a small number of genes including FT, the so-called florigen, which integrates environmental cues like ambient temperature. Nevertheless, detailed and functional studies about flowering time in Brassica crops are scarce. Here we study the role of the FT Brassica rapa homologues and the effect of high ambient temperature on flowering time in this crop. Phenotypic characterization and gene-expression analyses suggest that BraA.FT.a (BraA02g016700.3C) is decisive for initiating floral transition; consequently, braA.ft.a loss-of-function and hypomorphic mutations result in late flowering phenotypes. We also show that high ambient temperature delays B. rapa floral transition by reducing BraA.FT.a expression. Strikingly, these expression changes are associated with increased histone H2A.Z levels and less accessible chromatin configuration of the BraA.FT.a locus at high ambient temperature. Interestingly, increased H2A.Z levels at high ambient temperature were also observed for other B. rapa temperature-responsive genes. Previous reports delimited that Arabidopsis flowers earlier at high ambient temperature due to reduced H2A.Z incorporation in the FT locus. Our data reveal a conserved chromatin-mediated mechanism in B. rapa and Arabidopsis in which the incorporation of H2A.Z at FT chromatin in response to warm ambient temperature results in different flowering time responses. This work will help to develop improved Brassica crop varieties with flowering time requirements to cope with global warming. OPEN RESEARCH BADGES: This article has earned an Open Materials Badge for making publicly available the components of the research methodology needed to reproduce the reported procedure and analysis. Methods are available at protocols.iodx.doi.org/10.17504/protocols.io.zmff43n.