Sparrows are also picky eaters

On September 23, a global press conference held by Cell magazine introduced the research results of Chinese scientists on the molecular mechanism of sparrows feeding on different sorghum. Relevant research results were published online in Molecular Plant, a subjournal of Cell.

During the period from grain filling to ripening, a large number of sparrows migrated to the farmland to peck the seeds, which caused the seeds to be damaged and mildewed. At the same time, they spread various diseases and insect pests, resulting in different degrees of yield reduction. Some studies have reported that bird diseases can reduce the yield of sorghum by more than 50%. In the 1970s and 1980s, Europe, Africa and the United States spent nearly $1 billion a year studying how to prevent bird damage and avoid the huge agricultural losses it caused. Sparrows are very smart and alert, have strong recognition and memory, and are very alert. Previous researchers found that sparrows selectively preyed on different sorghum seeds through a large number of field observations: among 571 natural variation populations of sorghum, nearly 46.7% of the sparrows did not like sorghum seeds. So what is the cause of sparrows'picky eating behavior like human beings? Can the analysis of this problem provide a new perspective for the prevention and control of crop bird damage? Sorghum is widely used in feed, energy and fuel because of its excellent drought and waterlogging resistance, saline-alkali, barrenness and huge biomass. Up to now, sorghum is still the staple food crop for more than 500 million people in arid and semi-arid regions of the world due to its stress resistance. Previously, it was generally believed that the higher the degree of enclosure, spike type, awn, seed coat color and tannin content of sorghum, the more resistant to birds. However, the molecular mechanism of how sorghum itself resists bird damage remains unclear.

Recently, Xie Qi's team from the State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, jointly tackled key problems with three other laboratories, and published a paper entitled Control of Bird Feeding Behavior by Tannin1 through Modulating the Biosynthesis of Polyphenols and Fatty Acid-De in Molecular Plant. Research paper by rived Volatiles in Sorghum. By means of macrogenomics, metabonomics, synthetic biology and animal behaviour, the molecular mechanism of anthocyanin and proanthocyanidin (Anthocyanin and PA) synthesis and aroma volatiles synthesis from fatty acid sources regulated by Tannin 1 loci in sorghum was revealed to explain the phenomenon of sparrow picking on sorghum. 。

Xie Qi's team first conducted a two-year, three-point, two-repeat phenotypic survey of birds eating or not eating in two different natural populations. A single major locus Tannin1 gene was detected in both populations by GWAS analysis (Fig. 1). Tannin 1 is a key gene controlling tannin synthesis in sorghum. At the same time, it was found that among the five traits of shell, spike type, awn, seed coat color and tannin content, only tannin content was significantly correlated with bird resistance in sorghum.

Six sorghum bird-resistant varieties (Bird-avoidance, Tannin 1) and 12 non-bird-resistant varieties (Bird-preference, tan1-a/b) were randomly selected for LC-MS determination of target metabolites in tannin synthesis mechanism. Flavonoids, flavane-3-ol, anthocyanins and proanthocyanidins were found to be significant in non-bird-resistant varieties. The decline of the book. The behavioral experiments of standard birds (sparrows) proved that anthocyanins and proanthocyanidins, the metabolites of sparrows, were the fundamental factors affecting the feeding behavior of sparrows.

There are various interactions between plants and animals. Plants can release aromatic volatiles as attractants to attract bees and other pollinators, or toxic substances and their precursor volatiles as warning agents against predators. In the field, sparrows are seldom seen before the filling stage of sorghum, but after the filling stage of sorghum, a large number of sparrows migrate to the farmland. Does this mean that the sorghum seeds at the filling stage also emit aromatic volatiles to attract sparrows? GC-MS analysis of sorghum grains at grain filling stage showed that 9 volatiles with aromatic odor accumulated significantly in non-resistant bird species. Further, the sparrow behavioral experiments directly proved that hexanal and 1-octene-3-ol volatiles could indeed be used as attractants to attract sparrows to feed. These short-chain volatiles have been proved to be produced through the direct regulation of SbGL2 gene expression by Tannin 1/Myb/bHLH transcription complex, and ultimately through the degradation of LOX pathway.

In conclusion, this study reveals that Tannin 1 produces high tannin content and low concentration of aromatic volatiles by participating in the molecular mechanism of regulating both tannin synthesis and volatile synthesis from fatty acid sources, thus avoiding and defending sparrows to achieve bird resistance. This research not only provides important genetic resources for breeding new sorghum bird-resistant varieties, but also provides a new solution for using tannin to design and develop new green pesticides to control agricultural bird damage.