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Fatty acid (FA) composition determines the quality of oil from oilseed crops, and thus is a major target for genetic improvement. FAD2 (Fatty acid dehydrogenase 2) and FAE1 (fatty acid elongase 1) are critical FA synthetic genes, and have been the focus of genetic manipulation to alter fatty acid composition in oilseed plants. In this study, to improve the nutritional quality of rapeseed cultivar CY2 (about 50% oil content; of which 40% erucic acid), we generated novel knockout plants by CRISPR/Cas9 mediated genome editing of BnFAD2 and BnFAE1 genes. Two guide RNAs were designed to target one copy of the BnFAD2 gene and two copies of the BnFAE1 gene, respectively. A number of lines with mutations at three target sites of BnFAD2 and BnFAE1 genes were identified by sequence analysis. Three of these lines showed mutations in all three target sites of the BnFAD2 and BnFAE1 genes. Fatty acid composition analysis of seeds revealed that mutations at all three sites resulted in significantly increased oleic acid (70–80%) content compared with that of CY2 (20%), greatly reduced erucic acid levels and slightly decreased polyunsaturated fatty acids content. Our results confirmed that the CRISPR/Cas9 system is an effective tool for improving this important trait.

In rapeseed (Brassica napus L.), leaf margins are variable and can be entire, serrate, or lobed. In our previous study, the lobed-leaf gene (LOBED-LEAF 1, BnLL1) was mapped to a 32.1 kb section of B. napus A10. Two LMI1-like genes, BnaA10g26320D and BnaA10g26330D, were considered the potential genes that controlled the lobed-leaf trait in rapeseed. In the present study, these two genes and another homologous gene (BnaC04g00850D) were transformed into Arabidopsis thaliana (L.) Heynh. plants to identify their functions. All three LMI1-like genes of B. napus produced serrate leaf margins. The expression analysis indicated that the expression level of BnaA10g26320D determined the difference between lobed- and entire-leaved lines in rapeseed. Therefore, it is likely that BnaA10g26320D corresponds to BnLL1.

The lobed-leaf character is a clearly recognizable morphologic trait in rapeseed (Brassica napus L.) that has potential advantages in hybrid production. The present study was carried out to analyze the effect of lobed-leaf trait on agronomic traits and to fine map the LOBED-LEAF 1 (BnLL1) gene in B. napus. The lobed-leaf line Yuye 87 and entire-leaf cultivar Zheyou 50 were used to produce four F2 and eight BC1 populations for genetic analysis. Multiple comparison analysis between lobed-leaf character and agronomic traits was carried out in two F2 populations of reciprocal crosses between Yuye 87 and Zheyou 50. Results show that the lobed-leaf phenotype is controlled by a single an incomplete dominant gene and has no significant adverse effects on 10 main agronomic traits. The location of BnLL1 gene was narrowed down to a 36.7-kb homologous region of B. rapa between genes Bra009506 and Bra009511. On the basis of the annotation of orthologous genes in Arabidopsis, Bra009510 is considered to be a promising candidate for BnLL1 gene. The AT5G03790 is the orthologous gene of Bra009510 in Arabidopsis thaliana, with known functions in the formation of simple serrated leaves and in the suppression of bract formation. It is suggested that previously described lobed-leaf gene BnMOSAICLEAF (BnML) and the BnLL1 are the same genes controlling the lobed-leaf phenotype in B. napus, whereas the lobed-leaf gene BcLEAFLOBED 1 (BcLL1) is their homologue in Brassica campestris ssp. chinensis. These findings will facilitate the cloning and functional identification of the BnLL1 gene in future studies.

Increasing seed oil content has become one of the most important breeding criteria in rapeseed (Brassica napus). However, oil content is a complex quantitative trait. QTL mapping in a double haploid population (SG population) emerging from a cross between a German (Sollux) and Chinese (Gaoyou) cultivars revealed one QTL for oil content on linkage group A1 (OilA1), which was mapped to a 17 cM genetic interval. To further validate and characterize the OilA1, we constructed a high-resolution map using B. rapa sequence resources and developed a set of near-isogenic lines (NILs) by employing a DH line SG-DH267 as donor and Chinese parent Gaoyou as recurrent background. The results showed highly conserved synteny order between B. rapa and B. napus within the linkage group A1 and revealed a possible centromere region between two markers ZAASA1-38 and NTP3 (2.5 cM). OilA1 was firstly validated by 250 BC5F2 plants and was confirmed in a 10.6 cM interval between the markers ZAASA1-47 and ZAASA1-77. Further substitution mapping was conducted by using two generations of QTL-NILs, 283 lines from eight BC5F3:4 families and 428 plants from six BC5F4 sub-NILs and thus narrowed the OilA1 interval to 6.9 cM and 4.3 cM (1.4 Mb), respectively. Field investigations with two replications using homozygous BC5F3:4 sister sub-NILs indicated that NILs, which carry a Sollux chromosome segment across the target region showed significant higher oil content (1.26 %, p

Lintless mutant is a super-short fiber mutant in upland cotton only 4–8 mm in fiber length and also named Ligon cotton controlled by one dominant geneLi 1. Fiber ultrastructure of the mutant (Li 1) and its wild type (li 1)in situ andin vitro was observed under an electron microscope to understand its cytological characteristics during the fiber cell elongation. The results showed that the mutant fiberin situ had thinner cytoplasm, more small vacuoles, less mitochondria, Gllgi apparatus and endoplasmic reticula, and there were more starch granules which were free or packed in the amyloplast beside the cell wall than that of wild type. It was indicated that scarcity of functional organelles and disability of transformation from starch to sugar might be associated with the fact that the mutant fiber cell was aborted too early to elongate into normal length. Mutant ovule in some media containing GA3 could produce a kind of huge callus that grew faster than normal ovules. The callus was covered with many white, loose, and semitransparent fiber-like cells that apt to get off from ovule. These fiber-like cells were multicellular fibers generated by cell division and had black dots just like pigment glands in the stem and leaf of cotton. There were lots of micro-tubes beside cytoplasm membrane of the multicellular fiber, which were thought to be primary preparation for second wall deposition of multicellular fiber. It was indicated that GA3 might induce the expression of gene(s) that kept inactive in the field condition and then stimulate the original fiber cellin vitro to undergo division again.