MicroRNA528 Affects Lodging Resistance of Maize by Regulating Lignin Biosynthesis under Nitrogen-Luxury Conditions

Abstract

Lodging under nitrogen (N)-luxury conditions substantially reduces crop yield and seed quality. However, the molecular mechanisms of plant lodging resistance remain largely unclear, especially in maize. We report here that the expression of ZmmiR528, a monocot-specific microRNA, is induced by N luxury but reduced by N deficiency. We show by the thioacidolysis and acetyl bromide analysis that N luxury significantly reduces the generation of H, G, and S monomers of the lignin as well as its total content in maize shoots. We further demonstrate that ZmLACCASE3 (ZmLAC3) and ZmLACCASE5 (ZmLAC5), which encode the copper-containing laccases, are the targets of ZmmiR528. In situ hybridization showed that ZmmiR528 is mainly expressed in maize vascular tissues. Knockdown of ZmmiR528 or overexpression of ZmLAC3 significantly increased the lignin content and rind penetrometer resistance of maize stems. In contrast, transgenic maize plants overexpressing ZmmiR528 had reduced lignin content and rind penetrometer resistance and were prone to lodging under N-luxury conditions. RNA-sequencing analysis revealed that ZmPAL7 and ZmPAL8 are upregulated in transgenic maize lines downregulating ZmmiR528. Under N-luxury conditions, the expression levels of ZmPALs were much higher in ZmmiR528-knockdown lines than in the wild type and transgenic maize lines overexpressing ZmmiR528. Taken together, these results indicate that, by regulating the expression of ZmLAC3 and ZmLAC5, ZmmiR528 affects maize lodging resistance under N-luxury conditions.

Stalk Bending Strength is Strongly Associated with Maize Stalk Lodging Incidence Across Multiple Environments

“…Our finding that increased lignification of stalk cell walls is negatively associated with stalk lodging incidence is contrary to some studies which reported a positive impact of this secondary metabolite (Tripathi et al, 2003;Dorairaj et al, 2017;Sun et al, 2018). While this result seems counter-intuitive, there may be a simple explanation.…”

Large scale genome-wide association study reveals that drought induced lodging in grain sorghum is associated with plant height and traits linked to carbon remobilisation

“…Lodging resistant sorghum generally have more lignification, both in the number of cells with lignified walls and in the degree of lignification in the epidermis, sub-epidermis, and vascular bundles (Schertz and Rosenow 1977). Similar results have been previously observed in maize, with reduced lignin content in the stem resulting in increased stalk lodging (Sun et al 2018). More recently, Zhang et al (2020) reported that downregulation of a maize gene, stiff1 , resulted in thicker stalk cell walls with increased cellulose and lignin, which improved stalk strength and reduced lodging.…”

MicroRNA528, a hub regulator modulating ROS homeostasis via targeting of a diverse set of genes encoding copper‐containing proteins in monocots

“…Polyphenol oxidase is a Cu‐containing oxidase in a tetramer structure containing four Cu atoms per molecule, also referred to as tyrosinases (Vamos‐Vigyazo, ; Mayer, ). By contrast to the targeting of PPO genes by miR528 in banana, it has been reported that miR528 targets an ascorbate oxidase ( AAO ) and two laccase ( LAC ) genes in rice and maize, respectively (Wu et al ., ; Sun et al ., ); these genes belong to multicopper oxidase as PPO. Similarly, in creeping bentgrass miR528 can target AsAAO and AsCBP1 (encoding a Cu‐containing protein) (Yuan et al ., ).…”

“…In rice, miR528 is involved in antiviral defense by targeting L-ascorbate oxidase (also called L-ascorbic acid oxidase) gene, thereby reducing the accumulation of ROS (Wu et al, 2017). However, miR528 in maize affects lodging resistance by regulating the expression of two LAC genes (Sun et al, 2018). Interestingly, here it was found that miR528 targets PPO genes in banana, another monocot species, and five of them bear a miR528 target site (alignment score ≤ 5) in the coding region near the 5 0 end (Fig.…”

“…In addition, several species-or lineage-specific miRNAs identified from different plant species belong to this group. These include miR528 in rice and maize, miR1073 in moss and miR1444 in poplar (Lu et al, 2011;Higashi et al, 2013;Wu et al, 2017;Sun et al, 2018). miR528 has been reported to be involved in multiple plant stress responses (Li et al, 2013;Chavez-Hernandez et al, 2015;Sharma et al, 2015;Ragupathy et al, 2016).…”