The Metabolic Basis of Pollen Thermo-Tolerance: Perspectives for Breeding

Abstract

Crop production is highly sensitive to elevated temperatures. A rise of a few degrees above the optimum growing temperature can lead to a dramatic yield loss. A predicted increase of 1–3 degrees in the twenty first century urges breeders to develop thermo-tolerant crops which are tolerant to high temperatures. Breeding for thermo-tolerance is a challenge due to the low heritability of this trait. A better understanding of heat stress tolerance and the development of reliable methods to phenotype thermo-tolerance are key factors for a successful breeding approach. Plant reproduction is the most temperature-sensitive process in the plant life cycle. More precisely, pollen quality is strongly affected by heat stress conditions. High temperature leads to a decrease of pollen viability which is directly correlated with a loss of fruit production. The reduction in pollen viability is associated with changes in the level and composition of several (groups of) metabolites, which play an important role in pollen development, for example by contributing to pollen nutrition or by providing protection to environmental stresses. This review aims to underline the importance of maintaining metabolite homeostasis during pollen development, in order to produce mature and fertile pollen under high temperature. The review will give an overview of the current state of the art on the role of various pollen metabolites in pollen homeostasis and thermo-tolerance. Their possible use as metabolic markers to assist breeding programs for plant thermo-tolerance will be discussed.

HsfA2 Controls the Activity of Developmentally and Stress-Regulated Heat Stress Protection Mechanisms in Tomato Male Reproductive Tissues

“…In turn, alterations in the abundance of metabolites in anthers can influence both pollen development at physiological conditions and thermotolerance because developing pollen are highly dependent on supply of nutrients and metabolites from surrounding sporophytic tissues (Paupière et al, 2014). We performed nontargeted metabolomic profiling by gas chromatography coupled to mass spectrometry of control and stressed anthers from wild-type and A2AS-3 plants to examine whether HsfA2 suppression influences the primary metabolite composition of these tissues.…”

Identification of metabolites involved in heat stress response in different tomato genotypes

“…rice (Saragih et al 2013), sorghum (Prasad and Djanaguiraman 2011) and tomato (Firon et al 2006)). To understand the dynamic processes and key steps leading to the development of a mature and fertile pollen grain, several studies focussed on the analysis of transcripts, proteins and metabolites in pollen (Rutley and Twell 2015, Muschietti et al 1994, Paupière et al 2014. However, comprehensive metabolomics of pollen grains, such as large-scale untargeted LCMS or GCMS approaches, is not well developed compared to other omics technologies (figure 1).…”

“…Data on secondary metabolites in developing pollen are still limited and only a few targeted approaches have been used in the past (Paupière et al 2014). Isomers of each conjugated polyamine were summed up to represent the total abundance of each conjugated form.…”

“…An exploration of the primary metabolome of mature anthers of rice genotypes with contrasting tolerance to heat and drought stress also suggested that the sugar metabolism is a key factor in maintaining fertility under changing temperatures . Although great attention has been paid to sugar metabolism, other metabolites such as flavonoids and polyamines also play an important role in the development of a mature and fertile pollen grain (Paupière et al 2014). The ability of the anther to maintain metabolic homeostasis during abiotic stress is likely to be one of the main factors affecting the final quality of the mature pollen.…”

“…For instance, flavonoids and polyamines can act as scavengers of reactive oxygen species (ROS) (Rice- Evans et al 1996;Ha et al 1998). Despite these examples, the current knowledge on the role and importance of primary and secondary metabolites during pollen development is still limited (reviewed by Paupière et al 2014). …”