Abstract:

Soybean, oilseed rape, peanut, and so on, are important resources of vegetable oil for human beings. Cultivation and production of these oil crops are expected to increase due to continuous population growth, which poses a challenge to the genetic improvement of oil crops. With reference genomes of several oil crops sequenced and genetic transformation and gene editing tools readily available, the basic and applied researches of oil crops come to a functional genomic era integrating multiple approaches.

Plants measure day length (photoperiod) to determine when to flower and, thus, increase their chance of reproductive success. Soybean is one of the two plant species first discovered to have a photoperiodic response by Garner and Allard 100 years ago (Garner and Allard, 1920). Photoperiodic flowering is especially important for high yield production and broad latitude adaptation of soybean. In this issue, Lin et al. (2021) review the recent progress in dissecting the genetic regulatory network of photoperiodic flowering and provide a reference for molecular design and breeding of high yield soybean. Moreover, Fang et al. (2021) identify that the two major long-juvenile (LJ) loci, J and E6, are allelic. E6 is a loss-of-function allele, which carries a retrotransposon inside J, one of the components of soybean evening complex. Also revealed in this issue are the genetic and biochemical interactions among soybean growth habit and flowering timing pathways, where Yue et al. (2021) show that Dt1 and FT5a compete for physical binding to FDc1, regulate the expression of AP1, and control vegetative-to-reproductive transition of shoot apical meristem.

The root microbiome, also known as the rhizosphere microbiome, is the microorganisms associated with plant roots. These microorganisms could be beneficial, detrimental, or neutral to plant development and/or nutrients absorption. Wang et al. explore the microbial strains associated with soybean roots (2021). Potential beneficial strains were selected and constructed as synthetic communities, which improve soybean growth and nutrients usage both under lab condition and in field test.

Triacylglycerols (TAGs) are major components of soybean oil. In an attempt to increase oil content of soybeans, Zhao et al. (2021) engineered to overexpress a glycerol-3-phosphate dehydrogenase, encoded by GmGPDHp1, which significantly increase the content of TAG precursor, glycerol-3-phosphate (G3P), and eventually unsaturated fatty acids, without compromising the seed protein content and yield. Therefore, manipulation of G3P metabolism could be an effective strategy to improve soybean oil content.

In soybean, utilization of heterosis to improve yield lags far behind rice, maize and other crops of grass family. Male sterile soybean mutant and its causal gene are potential tools for utilizing heterosis. Nadeem et al. (2021) demonstrated that loss-of-function of a kinesin-like protein coding gene, GmMs1, compromised the pollen development and led to resulting in male sterility.

Studies on soybean, such as circadian sensing, photoperiodism adaptation, vegetative-to-reproductive growth transition, fat metabolism, gamete development, and root microbiota, not only deepen our understanding of the plant kingdom but also provide guidance to fulfill the improvement of oil crops. Future research would see the translation of this knowledge to targeted molecular design breeding of varieties with higher yield and better qualities.