Senescence, nutrient remobilization, and yield in wheat and barley

Abstract

Cereals including wheat and barley are of primary importance to ensure food security for the 21st century. A combination of lab- and field-based approaches has led to a considerably improved understanding of the importance of organ and particularly of whole-plant (monocarpic) senescence for wheat and barley yield and quality. A delicate balance between senescence timing, grain nutrient content, nutrient-use efficiency, and yield needs to be considered to (further) improve cereal varieties for a given environment and end use. The recent characterization of the Gpc-1 (NAM-1) genes in wheat and barley demonstrates the interdependence of these traits. Lines or varieties with functional Gpc-1 genes demonstrate earlier senescence and enhanced grain protein and micronutrient content but, depending on the environment, somewhat reduced yields. A major effort is needed to dissect regulatory networks centred on additional wheat and barley transcription factors and signalling pathways influencing the senescence process. Similarly, while important molecular details of nutrient (particularly nitrogen) remobilization from senescing organs to developing grains have been identified, important knowledge gaps remain. The genes coding for the major proteases involved in senescence-associated plastidial protein degradation are largely unknown. Membrane transport proteins involved in the different transport steps occurring between senescing organ (such as leaf mesophyll) cells and protein bodies in the endosperm of developing grains remain to be identified or further characterized. Existing data suggest that an improved understanding of all these steps will reveal additional, important targets for continued cereal improvement.

Mapping QTL for stay-green and agronomic traits in wheat under diverse water regimes

“…It has been observed in sorghum that during the grain-filling period under water stress conditions, genotypes possessing this trait maintain more photosynthetically active leaf areas than genotypes lacking it (Borrell et al 2000b;Rosenow et al 1983). Stay-green also plays an important role during the grain filling stage in wheat when assimilation is limited due to water stress (Distelfeld et al 2014). Along with other environmental constraints, wheat production in arid and semi-arid regions of the world is mainly limited by water stress, which causes premature senescence that results in lower grain yield and poor quality.…”

JIP60-mediated, jasmonate- and senescence-induced molecular switch in translation toward stress and defense protein synthesis

“…In fact, under optimal growth conditions, delaying the onset of senescence was shown to be positively correlated with grain yield (48). However, developmentally programmed senescence is essential for remobilization of reserves from source to sink organs.…”

Roles of C1A peptidases during barley leaf senescence mediated by abiotic stresses

“…Improvement of cereal cultivars requires a delicate balance among senescence timing, grain nutrient content, NUE, and yield (Distelfeld et al, 2014). The physiological stage at which a plant faces a given stress will largely influence upon the activation and progression of the senescence programs, determining the efficiency in the remobilization of nutrients as a strategy for survival.…”

“…belongs to the NAC family of TF, which seems to be up-regulated in many expression studies in response to senescence in both cereals (Gregersen, 2011), pointing these members as ideal candidates involved in senescence regulation (Gregersen, 2011;Distelfeld et al, 2014;Christiansen et al, 2016). In fact, it was proposed that NAC TF might be associated with ABA signaling in plants (Jensen et al, 2007).…”

“…Nitrogen remobilization during senescence, especially in cereals like barley and wheat, has captured the attention of numerous multidisciplinary groups (Gregersen et al, 2008;Distelfeld et al, 2014). Apart from those reports researching over specific genes, such as those encoding proteases and cystatins, other papers use a wide omics approach to identify abiotic stress-responsive genes (reviewed in Gürel et al, 2016).…”