No abstract

Interrogative proteome analyses are used to identify and quantify the expression of proteins involved in heat tolerance and to identify associated physiological processes in heat-stressed plants. The objectives of the study were to identify and quantify the expression of proteins involved in heat tolerance and to identify associated physiological processes in chickpea (Cicer arietinum L.) heat-tolerant (Acc#7) and sensitive genotype (Acc#8) from a field study. Proteomic and gene ontological analyses showed an upregulation in proteins related to protein synthesis, intracellular traffic, defence and transport in the heat-tolerant genotype compared to the susceptible one at the warmer site. Results from KEGG analyses indicate the involvement of probable sucrose-phosphate synthase (EC 2.4.1.14) and sucrose-phosphate phosphatase (EC 3.1.3.24) proteins, that were upregulated in the heat-tolerant genotype at the warmer site, in the starch and sucrose pathway. The presence of these differentially regulated proteins including HSP70, ribulose bisphosphate carboxylase/oxygenase activase, plastocyanin and protoporphyrinogen oxidase suggests their potential role in heat tolerance, at flowering growth stage, in field-grown chickpea. This observation supports unaltered physiological and biochemical performance of the heat-tolerant genotypes (Acc#7) relative to the susceptible genotype (Acc#8) in related studies (Makonya et al. 2019). Characterisation of the candidate proteins identified in the current study as well as their specific roles in the tolerance to heat stress in chickpea are integral to further crop improvement initiatives.

Heat and drought stresses are two abiotic factors that often occur simultaneously and are predicted to increase, consequently hampering plant growth. Response of different species to either stresses is well documented but information on the response of the same genotypes to both stresses in chickpea (Cicer arietinum L.) is limited. We aimed to determine whether previously noted heat‐stress‐tolerant genotype (Acc#7) is drought tolerant, that heat‐sensitive genotype (Acc#8) is drought sensitive, and whether intermittent moisture supply at vegetative stage would induce priming effect to later drought at flowering. At vegetative stage, plants were divided into three groups, nonstressed (watered to 75% field capacity [FC], severe water stress (moisture withholding for 14 d), and treated to 40% FC throughout the experiment (mild stress), with recovery for the severely stressed plants after which they were stressed (double stress) at flowering. Drought treatments at vegetative and flowering growth stages decreased physiological parameters and biomass accumulation in both genotypes except low water supply at 40% FC that decreased biomass in Acc#7 but not Acc#8. Double‐drought stress resulted in priming effect in Acc#7, having higher biomass, chlorophyll fluorescence, stomatal conductance (gs), net photosynthesis, and relative water content (RWC) vs. the introduction of stress only at flowering growth stage as well as in comparison with Acc#8. These results showed that both Acc#7 and Acc#8 are sensitive to drought, whereas after priming, Acc#7 is better acclimated to drought than Acc#8 associated with osmotic adjustment on leaf RWC and higher capacity to protect photosynthetic activity, making Acc#7 potentially ideal for areas associated with intermittent drought spells.

Desiccation tolerance evolved recurrently across diverse plant lineages to enable survival in water limited conditions. Many resurrection plants are polyploid and several groups have hypothesized that polyploidy enabled the evolution of desiccation tolerance. However, due to the vast evolutionary divergence between resurrection plant lineages, the rarity of desiccation tolerance, and the prevalence of polyploidy in plants, this hypothesis has been difficult to test. Here, we surveyed variation in morphological, reproductive, and desiccation tolerance traits across natural populations of a single species that has differing ploidies and tested for links between polyploidy and resilience. We sampled multiple populations of the resurrection grassMicrochloa caffraacross an environmental gradient ranging from mesic to xeric in South Africa. We describe two distinct ecotypes ofM. caffrathat occupy different ends of the environmental gradient and exhibit consistent differences in ploidy, morphological, reproductive, and desiccation tolerance traits in both field and common growth conditions. Interestingly, plants with more polyploid genomes were consistently more desiccation tolerant, less reproductive, and larger than plants with smaller genomes and lower ploidy. These data suggest that polyploidy enhances desiccation tolerance and that stronger selective pressures in increasingly xeric sites may play a role in maintaining and increasing desiccation tolerance.