Genotype-dependent response to water deficit: increases in maize cell wall digestibility occurs through reducing both p-coumaric acid and lignification of the rind

Abstract

Introduction: The compositional dynamics of the cell wall are influenced by drought, and it has been demonstrated that water deficit induces significant changes in its main components. Moreover, changes in cell wall concentration and distribution in response to water deficit affect maize degradability.

Material and methods: This study presents a histological and biochemical analysis of thirteen maize inbred lines, evaluated over two years in Pobra de Brollón (Spain) and Mauguio (France) under contrasting water availability conditions. Our aim was to investigate the environmental and genotypic impacts on histological and biochemical profiles, to assess in vitro cell wall digestibility under water deficit, and to explore how these responses relate to changes in cell wall composition and structure.

Results and discussion: Overall, we observed greater concentrations of p-coumaric acid under control conditions, with significant decreases in stressed conditions at each location. Histologically, we found an increase in non-lignified tissues under water deficit conditions across all tissues at each location as well. In terms of in vitro cell wall digestibility (IVCWRD), significant increases were detected in response to water deficit. Additionally, genotype-dependent response patterns were evident, revealing two distinct behavioural groups. Notably, in plastic genotypes, increases in IVCWRD in response to water deficit were concomitant to reductions in p-coumaric acid content and a decrease in red-stained lignified tissues in the rind. This study emphasizes the complex, genotype-dependent responses to water deficit, underscoring the important roles of plasticity and stability in shaping the impact on maize cell wall digestibility; paving the way to breed for adapted genotypes to face climate changes.

Keywords: cell wall digestibility; drought, maize; histology; lignification; p-coumaric acid.

Figure 1

Means comparison of p-coumaric acid and lignin-associated traits under different irrigation treatments. (A) pCA content (mg/g CW); (B) β-O-4-yield (nmol/mg lignin); and (C) Subunits S (nmol/mg lignin). Different letters indicate significant differences between conditions (p < 0.05).

Figure 2

Biplot of the PCA with K-means grouping for biochemical traits. Genotypes in each condition are represented by different colors: MWW in blue, PBWW in green, MWD1 in orange, MWD in red and PBWD in yellow, with groupings further illustrated by ellipses and symbols. Arrows indicate the contributions of variables to the PCA dimensions. IVCWRD, considered as a spectator variable, is represented with a striped arrow in blue.

Figure 3

Means comparison of histological traits under different irrigation treatments. (A) Red Rind tissues (% Rind surface); (B) Red Medullary tissues (% Medullary surface); and (C) Red Bundle tissues (% Bundle surface). Different letters indicate significant differences between conditions (p < 0.05).

Figure 4

Biplot of the PCA with K-means grouping for histological traits. Genotypes in each condition are represented by different colors: MWW in blue, PBWW in green, MWD1 in orange, MWD in red and PBWD in yellow, with groupings further illustrated by ellipses and symbols. Arrows indicate the contributions of variables to the PCA dimensions. IVCWRD, considered a spectator variable, is represented with a striped arrow in blue. General histological profile in (A) Well Watered conditions, (B) Intermediate Water Deficit, (C) Severe Water Deficit.

Figure 5

Means comparison of In Vitro Cell Wall Residue Digestibility under different irrigation treatments. Different letters indicate significant differences between conditions (p < 0.05).

Figure 6

Evolution of In Vitro Cell Wall Residue Digestibility in response to water deficit by genotype; at Mauguio on the right and Pobra de Brollón on the left. Control conditions in each location were considered 100%.

Figure 7

Co-variation between In Vitro Cell Wall Residue Digestibility, pCA and Red Rind tissues in response to water deficit. Red Rind tissues response is represented with a color range and genotypes are represented with different symbols. The treatments are represented in different sizes: MWD > MWD1 > PBWD.

Figure 8

Pearson correlations among biochemical and histological traits in response to water deficit. Only the response in water deficit conditions (MWD, MWD1, PBWD) was considered for the correlations. FAest: Ferulic acid esterified (mg/g CW); FAeth: Ferulic acid etherified (mg/g CW); pCA: p-coumaric acid (mg/g CW); ABL: Acetyl bromide lignin (mg/g CW); H: Subunit H (nmol/mg lignin); S: Subunit S (nmol/mg lignin); G: Subunit G (nmol/mg lignin); βO4yield: β-O-4-yield (nmol/mg lignin); MT_R_Mtot: Red Medullary tissues; RT_R_rtot: Red Rind tissues; BT_R_Btot: Red Bundle tissues; Stemarea: Stem cross-section area.

Figure 9

General biochemical and Histological profile of responding genotypes under well-watered (WW) and water deficit (WD) conditions.