Angiosperm fertilization has been a hot topic in the field of sexual plant reproduction. In recent years, great advances have been made in the studies on some critical steps, such as pollen tube guidance, polytubey block, and fertilization recovery system. However, most of these known mechanisms are synergid cell-based for ensuring successful double fertilization, the counterpart system based on central cell remains poorly understood. A recently published paper from Hongju Li’s lab revealed that the central cell could also secrete peptides as pollen tube attractants to guide the pollen tube entering embryo sac to ensure double fertilization. Interestingly, this mechanism is not synergid-dependent. Thus, the authors revealed a novel fertilization recovery system and bridged a gap in understanding the mechanism underlying double fertilization.

Life science is entering into the era of big data due to the rapid development of high-throughput omics technology. Multi-omics data such as genome, transcriptome, proteome, metabolome have greatly facilitated dissecting the complex and sophisticated regulatory networks of organisms. Recently, a collaborative team led by Lin Li, Fang Yang and Jianbing Yan from Huazhong Agricultural University constructed the first multi-omics integrative network map of maize. This map comprises over 30 000 genes and 2.8 million network edges at the levels of genome, transcriptome, translatome, and proteome, finally forming 1 412 regulatory modules. Using the integrative network map, the research team successfully predicted and confirmed five new functional genes regulating the development of tiller, lateral organ, and kernel in maize. Based on the integrative map and machine learning, the research team identified 2 651 maize flowering time genes that are enriched in eight candidate subnetworks. The biological functions of 20 flowering candidate genes were further validated using CRISPR/Cas9 gene editing technology and EMS mutants. Furthermore, evolutionary analysis of the integrative network map showed that the two subgenomes of maize had undergone a progressive functional differentiation from the levels of co-expression, co-translation to interactome. The construction of the multi-omics integrative network map represents an important breakthrough in maize functional genomics, which provides a new tool for cloning new genes, identifying novel molecular regulatory pathways, and revealing maize genome evolutionary features. This multi-omics integrative network map is a new key to decode maize functional genomics.

Optimal Balance between high yield and stress tolerance is the goal of breeding, which is related to the strategy in choice of both ways. The questions such as which negative regulators of stress tolerance affect yield and how they function are important issues for breeding. Over the past century, owing to the breeding of high-yield varieties, the maize yield has been tremendously increased, but this is accompanied with the increased sensitivity to environmental stresses, and the genetic mechanisms underlying this phenomenon remains elusive. This restricts the breeding of maize cultivars with both high yield and stress tolerance. Both yield traits and stress tolerance are complex quantitative traits, determined by the expression and regulation of a large number of genes. Small RNAs (sRNAs) are important gene expression regulators, and they are generated in large quantities from the maize genome. But the mechanisms underlying their regulation on crop stress responses and yield traits remain largely elusive. Recently, the group of Prof. Mingqiu Dai, collaborated with the groups of Prof. Lin Li and Prof. Feng Li at Huazhong Agricultural University, identified about ten-thousands of drought-responsive sRNAs and eQTLs associated with the expression of these sRNAs, by analyzing the sRNAome and transcriptome of a maize panel consisting 338 natural inbred lines grown under different environment conditions. They cloned an eQTL hotspot named DRESH8, which is a Transposable Element-mediated Inverted Repeat (TE-IR) in a length of about 21.4 kb. Genetic and molecular evidence showed that DRESH8-derived siRNAs directly inhibit the expression of the drought-resistant genes via a post-transcriptional silencing mechanism, and indirectly inhibit the expression of negative regulators of yield-related traits, thus negatively regulating drought response and positively regulate yield-related traits. Further analysis demonstrated that DRESH8 was selected during maize domestication and improvement. Their findings suggest that DRESH8 is a key genetic locus that balances maize yield and drought tolerance, and that IR-mediated balance between maize yield and drought resistance may be a universal mechanism. This study thus revealed a key genetic mechanism underlying balancing crop yield and environmental stress resistance at a genome-wide level, and provided a large number of valuable IR loci for breeding new maize varieties with both high yield and stress tolerance via genetic engineering approaches in the future.

Domestication of wild plants was crucial for human settlement and the development of civilization, which arose independently in many different geographic areas on different wild species. However, these crops underwent variant domestication process displaying the ‘domestication syndrome’ with a common suite of traits. The systematical analysis of convergent selection at genome level may provide important information and genetic resources for crop breeding. Recently, a team led by Xiaohong Yang and Jiansheng Li from Chinese Agricultural University and Jianbing Yan from Huazhong Agricultural University reported the genetic basis of convergent selection between maize and rice at both single gene and whole genome levels. Particularly, they found the maize KRN2 and rice OsKRN2 genes experienced convergent selection and regulated grain number and yield in a similar pathway. Moreover, they identified a large number of orthologous gene pairs that underwent convergent selection during maize and rice evolution, which were enriched in certain pathways including starch metabolism, sugar and coenzyme synthesis. This significant work not only cloned KRN2/OsKRN2 orthologous gene pairs with great value in maize and rice breeding, but also revealed the convergent selection between maize and rice at the genome level, providing critical foundations for studying the molecular basis of domestication syndrome and their applications in breeding practices.

Phosphorus is a macronutrient essential for plant growth and development, however, phosphate (Pi), the major form of phosphorus absorbed by plants, is quite limiting in soil. To cope with this nutritional stress, plants have evolved an array of adaptive responses, which are largely regulated by changing gene expression in response to Pi deficiency. The transcription factor, PHR1 plays a key role in regulating plant transcriptional response to Pi deficiency. Besides, most land plants can form symbiosis with arbuscular mycorrhizal (AM) fungi, through which plants can obtain Pi from soil more effectively. Recently, the research group of Ertao Wang of Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, reported that a PHR-centered gene regulatory network plays an essential role in promoting plant-AM symbiosis. Therefore, PHR not only functions in maintaining plant Pi homeostasis, but also in communicating with beneficial microorganisms in the environments, which provides another route for plants to obtain Pi from soil.