GmDNJ1, a type-I heat shock protein 40 (HSP40), is responsible for both Growth and heat tolerance in soybean.

Global warming poses severe threats to agricultural production, including soybean. One of the major mechanisms for organisms to combat heat stress is through heat shock proteins (HSPs) that stabilize protein structures at above-optimum temperatures, by assisting in the folding of nascent, misfolded, or unfolded proteins. The HSP40 subgroups, or the J-domain proteins, functions as co-chaperones. They capture proteins that require folding or refolding and pass them on to HSP70 for processing. In this study, we have identified a type-I HSP40 gene in soybean, GmDNJ1, with high basal expression under normal growth conditions and also highly inducible under abiotic stresses, especially heat. Gmdnj1-knockout mutants had diminished growth in normal conditions, and when under heat stress, exhibited more severe browning, reduced chlorophyll contents, higher reactive oxygen species (ROS) contents, and higher induction of heat stress-responsive transcription factors and ROS-scavenging enzyme-encoding genes. Under both normal and heat-stress conditions, the mutant lines accumulated more aggregated proteins involved in protein catabolism, sugar metabolism, and membrane transportation, in both roots and leaves. In summary, GmDNJ1 plays crucial roles in the overall plant growth and heat tolerance in soybean, probably through the surveillance of misfolded proteins for refolding to maintain the full capacity of cellular functions.

Fine mapping of Restorer-of-fertility in pepper (Capsicum annuum L.) identified a candidate gene encoding a pentatricopeptide repeat (PPR)-containing protein.

KEY MESSAGE: Using fine mapping techniques, the genomic region co-segregating with Restorer - of - fertility ( Rf ) in pepper was delimited to a region of 821 kb in length. A PPR gene in this region, CaPPR6 , was identified as a strong candidate for Rf based on expression pattern and characteristics of encoding sequence. Cytoplasmic-genic male sterility (CGMS) has been used for the efficient production of hybrid seeds in peppers (Capsicum annuum L.). Although the mitochondrial candidate genes that might be responsible for cytoplasmic male sterility (CMS) have been identified, the nuclear Restorer-of-fertility (Rf) gene has not been isolated. To identify the genomic region co-segregating with Rf in pepper, we performed fine mapping using an Rf-segregating population consisting of 1068 F2 individuals, based on BSA-AFLP and a comparative mapping approach. Through six cycles of chromosome walking, the co-segregating region harboring the Rf locus was delimited to be within 821 kb of sequence. Prediction of expressed genes in this region based on transcription analysis revealed four candidate genes. Among these, CaPPR6 encodes a pentatricopeptide repeat (PPR) protein with PPR motifs that are repeated 14 times. Characterization of the CaPPR6 protein sequence, based on alignment with other homologs, showed that CaPPR6 is a typical Rf-like (RFL) gene reported to have undergone diversifying selection during evolution. A marker developed from a sequence near CaPPR6 showed a higher prediction rate of the Rf phenotype than those of previously developed markers when applied to a panel of breeding lines of diverse origin. These results suggest that CaPPR6 is a strong candidate for the Rf gene in pepper.