Enhancing photosynthetic efficiency is a major goal for improving crop yields under agricultural field conditions and is associated with chloroplast biosynthesis and development.  In this study, we demonstrate that Golden2-like 1a (BnGLK1a) plays an important role in regulating chloroplast development and photosynthetic efficiency.  Overexpressing BnGLK1a resulted in significant increases in chlorophyll content, the number of thylakoid membrane layers and photosynthetic efficiency in Brassica napus, while knocking down BnGLK1a transcript levels through RNA interference (RNAi) had the opposite effects.  A yeast two-hybrid screen revealed that BnGLK1a interacts with the abscisic acid receptor PYRABACTIN RESISTANCE 1-LIKE 1–2 (BnPYL1–2) and CONSTITUTIVE PHOTOMORPHOGENIC 9 SIGNALOSOME 5A subunit (BnCSN5A), which play essential roles in regulating chloroplast development and photosynthesis.  Consistent with this, BnGLK1a-RNAi lines of B. napus display hypersensitivity to the abscisic acid (ABA) response.  Importantly, overexpression of BnGLK1a resulted in a 10% increase in thousand-seed weight, whereas seeds from BnGLK1a-RNAi lines were 16% lighter than wild type.  We propose that BnGLK1a could be a potential target in breeding for improving rapeseed productivity.  Our results not only provide insights into the mechanisms of BnGLK1a function, but also offer a potential approach for improving the productivity of Brassica species.

Rapeseed (Brassica napus L.) is the second most widely grown premium oilseed crop globally, mainly for its vegetable oil and protein meal.  One of the main goals of breeders is producing high-yield rapeseed cultivars with sustainable production to meet the requirements of the fast-growing population.  Besides the pod number, seeds per silique (SS), and thousand-seed weight (TSW), the ovule number (ON) is a decisive yield determining factor of individual plants and the final seed yield.  In recent years, tremendous efforts have been made to dissect the genetic and molecular basis of these complex traits, but relatively few genes or loci controlling these traits have been reported thus far.  This review highlights the updated information on the hormonal and molecular basis of ON and development in model plants (Arabidopsis thaliana).  It also presents what is known about the hormonal, molecular, and genetic mechanism of ovule development and number, and bridges our understanding between the model plant species (A. thaliana) and cultivated species (B. napus).  This report will open new pathways for primary and applied research in plant biology and benefit rapeseed breeding programs.  This synopsis will stimulate research interest to further understand ovule number determination, its role in yield improvement, and its possible utilization in breeding programs. 

Rapeseed (Brassica napus L.) is one of the most important oilseed crops worldwide.  Development of rapeseed varieties with high-quality oil is a long-term breeding goal.  Reducing the contents of palmitic acid, the main saturated fatty acid in rapeseed oil, could greatly improve oil quality.  Here, we performed genome-wide association study (GWAS) and transcriptome-wide association study (TWAS) of seed palmitic acid content (SPAC) using 393 diverse B. napus accessions.  Four genes (BnaA08.DAP, BnaA08.PAA1, BnaA08. DUF106, and BnaC03.DAP) were identified by both GWAS and TWAS.  The transcripts per million (TPM) values of these candidate genes at 20 and 40 days after flowering (DAF) were significantly correlated with SPAC in this association panel.  Based on genetic variation in the candidate genes, we identified four low-SPAC haplotypes by combining candidate gene association analysis and haplotype analysis.  Brassica napus accessions carrying low-SPAC haplotypes had lower SPAC than those carrying high-SPAC haplotypes without affecting seed oil content, seed protein content, or seed yield.  Based on the functional single-nucleotide polymorphism (SNP) chrA08_9529850 (C/A) in the promoter of BnaA08.DUF106, we developed a molecular marker (Bn_A8_SPAC_Marker) that could be used to facilitate breeding for low SPAC in B. napus.  Our findings provide valuable information for studying the genetic control of SPAC in B. napus.  Moreover, the candidate genes, favorable haplotypes, and molecular marker identified in this study will be useful for breeding low-SPAC B. napus varieties.