Abscisic acid collaborates with lignin and flavonoid to improve pre‐silking drought tolerance by tuning stem elongation and ear development in maize (Zea mays L.)

Abstract

SUMMARY Drought is a major abiotic stress reducing maize (Zea mays) yield worldwide especially before and during silking. The mechanism underlying drought tolerance in maize and the roles of different organs have not been elucidated. Hence, we conducted field trials under pre‐silking drought conditions using two maize genotypes: FM985 (drought‐tolerant) and ZD958 (drought‐sensitive). The two genotypes did not differ in plant height, grain number, and yield under control conditions. However, the grain number per ear and the yield of FM985 were 38.1 and 35.1% higher and plants were 17.6% shorter than ZD958 under drought conditions. More 13C photosynthates were transported to the ear in FM985 than in ZD958, which increased floret fertility and grain number. The number of differentially expressed genes was much higher in stem than in other organs. Stem–ear interactions are key determinants of drought tolerance, in which expression of genes related to abscisic acid, lignin, and flavonoid biosynthesis and carbon metabolism in the stem was induced by drought, which inhibited stem elongation and promoted assimilate allocation to the ear in FM985. In comparison with ZD958, the activities of trehalose 6‐phosphate phosphatase and sucrose non‐fermentation‐associated kinase 1 were higher in the stem and lower in the kernel of FM985, which facilitated kernel formation. These results reveal that, beyond the ear response, stem elongation is involved in the whole process of drought tolerance before silking. Abscisic acid together with trehalose 6‐phosphate, lignin, and flavonoid suppresses stem elongation and allocates assimilates into the ear, providing a novel and systematic regulatory pathway for drought tolerance in maize.

Identification of a novel marker and its associated laccase gene for regulating ear length in tropical and subtropical maize lines

“…6 b, Supplementary Table 5 ). Given that POD is also the key enzyme in the final stage of the plant lignin synthesis pathway (Dong and Lin 2020 ; Gao et al 2023 ), we measured POD activity as well from the tip and midsection ears of the six parental lines at the V9, tasseling, and silking stages. The results exhibited diverse trends in POD activities among different parental lines as the growth of the ears progressed.…”

“…Consequently, it is possible that in the samples, other laccases excluding ZmLac4 , exhibited high activities. POD and LAC are crucial enzymes involved in polymerizing lignin monomers during the later stages of the lignin synthesis pathway (Hoffmann et al 2020 ; Gao et al 2023 ), the genes regulating POD activity in TML418 may also contribute to ear elongation (Fig. 6 c).…”

FlbZIP12 gene enhances drought tolerance via modulating flavonoid biosynthesis in Fagopyrum leptopodum

“…Plants respond to drought stress by regulating ABA signal transduction and flavonoid biosynthesis ( Gao et al., 2023 ; Zhang et al., 2023 ). We showed here that FlbZIP12 may interact with the kinases SnRK2.2 and SnRK2.6 to upregulate RD29B and ERD1 expression to enhance F. leptopodum drought tolerance.…”

Systematic Identification and Functional Analysis of the Hypericum perforatum L. bZIP Gene Family Indicating That Overexpressed HpbZIP69 Enhances Drought Resistance

“…Subsequent experiments could explore whether the HpbZIP69 transcription factors bind to promoters and pertain to ABA-mediated transcriptional activation. In addition, ABA-mediated transcriptional activity is related to flavonoid synthesis [ 34 ], so whether HpbZIP69 plays a role in the flavonoid metabolism pathway could be explored, and the drought response mechanism of HpbZIP69 could be further elucidated.…”