Somatic embryogenesis from mature sorghum seeds: An underutilized genome editing recipient system.

Somatic embryogenesis is a process of cell totipotency in vitro, whereby an embryogenic cell develops from vegetative tissues rather than from zygotes after double fertilization. Sorghum is a recalcitrant crop in genetic transformation; previous recipient systems have usually been from immature zygotic embryos, which needed more time and labors to prepare. Here, an efficient 2,4-dichlorophenoxyacetic acid (2,4-D)-induced somatic embryogenesis system from mature sorghum seeds was introduced. 2,4-D can induce two types of calli from a plumular axis section. Low-concentration 2,4-D (e.g., 2 mg/L) induces white and loose non-embryogenic calli (type 1), while high-concentration 2,4-D (e.g., 8 mg/L) induces yellow and compact embryogenic calli (type 2), which can be clearly distinguished by Sudan red staining. Germinating seeds have a long 2-day window for SE induction. Somatic embryogenesis can be enhanced by HDAC inhibitor, trichostatin A (TSA), a histone deacetylase treatment, which shows more SE productivity and a bigger size. Importantly, this easily prepared protocol does not show obvious genotype dependency in sorghum hybrids. In this study, a high-concentration 2,4-D-induced SE system was established from mature sorghum seeds. This finding provides a technical option for the genome editing recipient in sorghum.

Combined transcriptomic and physiological metabolomic analyses elucidate key biological pathways in the response of two sorghum genotypes to salinity stress.

Sorghum is an important food crop with high salt tolerance. Therefore, studying the salt tolerance mechanism of sorghum has great significance for understanding the salt tolerance mechanism of C4 plants. In this study, two sorghum species, LRNK1 (salt-tolerant (ST)) and LR2381 (salt-sensitive (SS)), were treated with 180 mM NaCl salt solution, and their physiological indicators were measured. Transcriptomic and metabolomic analyses were performed by Illumina sequencing and liquid chromatography-mass spectrometry (LC-MS) technology, respectively. The results demonstrated that the plant height, leaf area, and chlorophyll contents in LRNK1 were significantly higher than in LR2381. Functional analysis of differently expressed genes (DEGs) demonstrated that plant hormone signal transduction (GO:0015473), carbohydrate catabolic processes (GO:0016052), and photosynthesis (GO:0015979) were the main pathways to respond to salt stress in sorghum. The genes of the two varieties showed different expression patterns under salt stress conditions. The metabolomic data revealed different profiles of salicylic acid and betaine between LRNK1 and LR2381, which mediated the salt tolerance of sorghum. In conclusion, LRNK1 sorghum responds to salt stress via a variety of biological processes, including energy reserve, the accumulation of salicylic acid and betaine, and improving the activity of salt stress-related pathways. These discoveries provide new insights into the salt tolerance mechanism of sorghum and will contribute to sorghum breeding.

Cell-penetrating peptide: A powerful delivery tool for DNA-free crop genome editing.

Genome editing system based on the CRISPR/Cas (clustered regularly interspaced short palindromic repeats) technology is a milestone for biology. However, public concerns regarding genetically modified organisms (GMOs) and recalcitrance in the crop of choice for regeneration have limited its application. Cell-penetrating peptides (CPPs) are derived from protein transduction domains (PTDs) that can take on various cargoes across the plant wall, and membrane of target cells. Selected CPPs show mild cytotoxicity and are a suitable delivery tool for DNA-free genome editing. Moreover, CPPs may also be applied for the transient delivery of morphogenic transcription factors, also known as developmental regulators (DRs), to overcome the bottleneck of the crop of choice regeneration. In this review, we introduce a brief history of cell-penetrating peptides and discuss the practice of CPP-mediated DNA-free transfection and the prospects of this potential delivery tool for improving crop genome editing.

Transcriptomic analysis of starch accumulation patterns in different glutinous sorghum seeds.

Sorghum is a high-quality raw material for brewing white wine, and the starch content in seeds has a large impact on brewing quality. Transcriptomic data obtained from a glutinous variety (Liaonian3) and a non-glutinous variety (Liaoza10) at 3, 18, and 30 days after pollination were analyzed to identify genes associated with starch accumulation. The amylopectin content was significantly higher in Liaonian3 compared to Liaoza10, but the amylose content and total starch content were lower. There were 6634 differentially expressed genes found in Liaoza10 between 3 and 18 d after pollination, and 779 differentially expressed genes between 18 and 30 d after pollination. In Liaonian3, there were 6768 differentially expressed genes between 3 and 18 d after pollination, and 7630 differentially expressed genes between 18 and 30 d after pollination. Genes were grouped by expression profiles over the three time points and the profiles were analyzed for enrichment of gene ontology terms and biochemical pathways. Profile 1 (decreasing expression from 3 to 30 d) for Liaoza10 was enriched in ribosomes, metabolic pathways, and carbon metabolic pathways. Profile 0 (decreasing expression from 3 to 18 d and consistent expression from 18 to 30 d) was enriched in pathways related to sugar or starch metabolism. Although the starch accumulation rate in Liaonian3 and Liaoza10 showed a profile of increasing and then decreasing, the expression of genes related to starch synthesis gradually decreased with time since pollination, demonstrating the complexity of starch synthesis. According to orthologous gene alignment and expression analysis, 19 genes such as entrzID_8068390 and entrzID_8066807 were found to be the key genes for starch synthesis and glutinous and non-glutinous differentiation in sorghum grains.

Regulation of photosynthetic material production by inter-root microbial extinction and metabolic pathways in sorghum under different nitrogen application patterns.

The development of nitrogen fertilizer green and efficient application technology by exploring the mechanism of efficient sorghum N use is important for sustainable development of sorghum industry as well as barren marginal land development and utilization. This study was conducted in 2018, 2019, and 2020 at Shenyang, China, using the nitrogen-efficient sorghum variety Liaonian No. 3 as material. The correlation between soil microbial species, diversity, and metabolic pathways with photosynthetic parameters and yield traits was analyzed to elucidate the mechanisms of nitrogen utilization and photosynthetic material production in sorghum under four fertilizer application patterns. The results showed that 17 populations of soil inter-root microorganisms were active in the organic fertilizer + 0 kg per hm2 of nitrogen (N0Y) model, and the abundance of two key populations, Comamonadaceae and Ellin5301, was significantly increased. Soil microorganisms regulated sorghum growth mainly through 30 pathways, focus including ko00540, ko00471, ko00072 and ko00550, of which ko02030 (Bacterial chemotaxis) and ko00072 (Synthesis and degradation of ketone bodies) played the most critical role. The functional analysis of soil microbial populations revealed that N0Y fertilizer model significantly reduced the intracellular trafficking, secretion. In addition, vesicular transport of microorganisms, amino acid transport and metabolism and nucleotide transport and metabolism played a key role in the regulation of population function. Overall, the N0Y model of N-efficient sorghum can achieve high levels of photosynthetic material production and higher yield formation through regulation of population activities and metabolic pathways of loamy microorganisms, resulting in reduced chemical N application and efficient green production of sorghum.

Interaction of genotype-ecological type-plant spacing configuration in sorghum [Sorghum bicolor (L.) Moench] in China.

Grain sorghum has been a significant contributor to global food security since the prehistoric period and may contribute even more to the security of both food and energy in the future. Globally, precise management techniques are crucial for increasing grain sorghum productivity. In China, with diverse ecological types, variety introduction occasionally occurs across ecological zones. However, few information is available on the effect of ecological type on genotype performance and how plant spacing configuration influences grain yield in various ecological zones. Hence, a series of two-year field experiments were conducted in 2020 and 2021 in four ecological zones of China, from the northeast to the southwest. The experiments included six widely adapted sorghum varieties under six plant spacing configurations (two row spacing modes: equidistant row spacing (60 cm) mode and wide (80 cm)-narrow (40 cm) row spacing mode; three in-row plant spacings: 10 cm, 15 cm, and 20 cm). Our results indicated that ecological type, variety, and plant spacing configuration had a significant effect on sorghum yield. Ecological type contributed the highest proportion to the yield variance (49.8%), followed by variety (8.3%), while plant spacing configuration contributed 1.8%. Sorghum growth duration was highly influenced by the ecological type, accounting for 87.2% of its total variance, whereas plant height was mainly affected by genotype, which contributed 81.6% of the total variance. All test varieties, developed in the south or north, can reach maturity within 94-108 d, just before fall sowing in central China. Generally, sorghum growth duration becomes longer when a variety is introduced from south to north. A late-maturing variety, developed in the spring sowing and late-maturing regions, possibly could not reach maturity in the early-maturing region. The row spacing modes had no significant affect on sorghum yield, but the equal-row spacing mode consistently caused higher yields with only one exception; this might imply that equal-row spacing mode was more advantageous for boosting sorghum yield potential. In contrast, decreasing in-row plant spacing showed significant positive linear associations with sorghum grain yield in most cases. In addition, these results demonstrated that sorghum is a widely adapted crop and enables success in variety introduction across ecological zones.

Responses of maize hybrids with contrasting maturity to planting date in Northeast China.

Maize sowing in semi-humid region of Jilin province is often delayed beyond the optimum planting time window because of soil water stress typically occurring before or during the planting season. Research was conducted at Lishu city, in Jilin province from 2009 through 2010 to determine the responses of maize hybrids with contrasting maturity to planting date. Three popular hybrids with contrasting different maturity, short-season hybrid Jidan27, mid-season hybrid Xianyu335, and full-season hybrid Zhengdan958 were planted in early May and mid-May and thinned to populations of 67,500 plants ha-1. The results showed that durations from emergence to silking stage for all the hybrids consistently shortened as the planting delayed, but interaction effects of hybrids, planting date and year existed for the duration of silking to physiological maturity stage. The longer maturity hybrid usually had grain yield advantage over earlier maturity hybrid when planting at early May, but the earlier maturity hybrid often showed a greater yield than longer maturity hybrid when planting was delayed. The highest yield occurred at the treatment combination of the mid-season hybrid and delayed planting date, and the shorter season hybrid typically showed stable and higher grain yield across planting dates. Changes in grain volume per unit of land area among hybrids and planting date treatment combination were consistent with the changes in grain yields, indicating that the yield is determined usually by the sink capacity. Further research is needed to evaluate the effects of hybrids maturity and planting date on maize under different planting densities.