Chinese scholars and overseas collaborators have made new progress in the research of the regulation mechanism of maize drought resistance and yield balance

Fig.
DRESH8 regulates maize yield and drought tolerance balance

With the support of the National Natural Science Foundation of China (approval numbers: 32061143031, 91940301, 92035302), the Dai Mingqiu research group of Huazhong Agricultural University, together with Li Feng, Li Lin's research group and Dr.
Sarah Hearne of CIMMYT (International Wheat and Maize Improvement Center), elaborated for the first time the genetic and molecular regulatory mechanisms of maize yield and drought resistance balance.
It lays a theoretical foundation and provides excellent genetic resources
for high-resistance, high-yield precision molecular design and breeding of maize.
The research results, titled "The role of transposon inverted repeats in balancing drought tolerance and yield-related traits in maize", were published in Nature on October 13, 2022.
Journal
of Nature Biotechnology.
Link to paper: _istranslated="1">.

Maize is the largest food crop in China and is crucial
to ensuring national food security.
Corn is sensitive to drought, and every year due to drought, China's corn production is greatly reduced and huge economic losses
are lost.
Over the past 100 years, breeders have greatly increased maize yields, but this has been accompanied by a significant decline in maize drought tolerance, indicating antagonism between yield traits and stress tolerance traits, and that the genetic loci that control the two are closely linked
on the genome.
How to break this chain and achieve the best balance between yield and resistance is a research direction of great application value in the field of crop breeding, and finding the negative regulatory site of drought stress response to control yield traits and revealing its genetic and molecular mechanism is a major bottleneck problem faced by high-yield and high-drought-resistant crop breeding
.

Based on the analysis of hundreds of small RNA (sRNA) expression groups and gene transcriptomes in natural populations of maize, the Dai Mingqiu team and collaborators cloned a superhotspot eQTLDRESH8 on chromosome 8 that regulates sRNA expression and drought specificity, which is a transposable element-inverted repeat (TE-IR)
。 The transgenic maize lacking DRESH8 was obtained by gene editing, and it was found that the transgenic maize was more drought-resistant than the wild-type control maize, and the sRNA produced was significantly reduced compared with the wild-type maize, indicating that DRESH8 was a causal variation site regulating drought resistance and sRNA expression variation in maize population
.
Yield surveys and evolutionary analysis found that DRESH8 mediates a selective balance between drought resistance and yield traits: in environments with abundant rainfall, farmers may choose to plant maize with DRESH8 to increase yields; In an arid environment, farmers chose to plant corn lacking DRESH8, which could remove the inhibition of drought-resistant genes in the sRNA produced by DRESH8, thereby improving the drought tolerance
of maize.
Further studies showed that genome-wide TE controlled the expression of about 42% of drought response sRNA by forming IR sequences, indicating that IR plays a wide range of roles
in maize drought response.
In addition, there are dozens of eQTL hotspots with TE-IR structural variations, and the potential target genes regulated by the generated sRNA are enriched into gene sets related to yield and stress resistance, indicating that TE-IR may have a universal role in regulating the balance of environmental adaptability and yield traits in maize (Figure).