Transcriptomic Response to Water Deficit Reveals a Crucial Role of Phosphate Acquisition in a Drought-Tolerant Common Bean Landrace

Abstract

Drought is one of the most critical factors limiting legume crop productivity. Understanding the molecular mechanisms of drought tolerance in the common bean is required to improve the yields of this important crop under adverse conditions. In this work, RNA-seq analysis was performed to compare the transcriptome profiles of drought-stressed and well-irrigated plants of a previously characterized drought-tolerant common bean landrace. The analysis revealed responses related with the abscisic acid signaling, including downregulation of a phosphatase 2C (PP2C) and an abscisic acid-8′ hydroxylase, and upregulation of several key transcription factors and genes involved in cell wall remodeling, synthesis of osmoprotectants, protection of photosynthetic apparatus, and downregulation of genes involved in cell expansion. The results also highlighted a significant proportion of differentially expressed genes related to phosphate starvation response. In addition, the moderate detrimental effects of drought in the biomass of these tolerant plants were abolished by the addition of phosphate, thus indicating that, besides the ABA-mediated response, acquisition of phosphate could be crucial for the drought tolerance of this common bean genotype. These results provided information about the mechanisms involved in drought response of common bean response that could be useful for enhancing the drought tolerance of this important crop legume.

Differential Regulation of Drought Responses in Two Phaseolus vulgaris Genotypes

“…In a previous study, several genes of the core ABA signaling were found to change in response to drought in the highly resistant PHA-0683 landrace [ 47 ]. To elucidate whether similar ABA-mediated responses take place in the PMB-0220 line, levels of relative expression of key genes for ABA synthesis (9-Cisepoxycarotenoid Dioxygenase, NCED), degradation ((+)-Abscisic acid 8’-Hydroxylase, ABA 8’H), ABA signaling (type 2C protein phosphatases, PP2Cs) and downstream responsive genes, as the proline synthesis (∆1-Pyrroline–5-Carboxylate Synthase, P5CS), were measured in samples of the two genotypes.…”

“…From these, landrace PHA-0683 ranked as a highly drought-resistant genotype, whereas PMB-0220 was a commercial high yielding line, that ranked as moderately resistant to drought conditions [ 39 ]. In a recent genome wide transcriptomic analysis in leaf tissue of PHA-0683 landrace, differential expression of key genes related with ABA-mediated responses and the regulation of senescence by drought was observed [ 47 ].…”

“…In a previous study, the transcriptome changes in response to drought showed down-regulation of genes coding for proteins that are repressors of ABA signaling, as the PP2Cs, and of ABA degradation, as ABA 8′ hydroxylase, suggesting that ABA-mediated responses were activated in PHA-0683 landrace. [ 47 ]. In this work we have compared the expression levels of genes coding for key enzymes in ABA synthesis, as the 9-cis-epoxycarotenoid dioxygenase (NCED) [ 55 ], signaling as phosphatase PP2C, degradation as ABA 8′ hydroxylase, and ABA-responsible genes, like the one coding P5CS, involved in the synthesis of proline.…”

“…On the other hand, the PMB-0220 line showed a good level of resistance to drought, although lower than that of PHA-0683 [ 12 , 39 , 40 ]. In addition, a genome wide transcriptomic analysis of differentially expressed genes under drought conditions in the resistant common bean PHA-0683 landrace, identified changes in ABA signaling-related genes and several key transcription factors known to regulate stress and developmental responses [ 47 ].…”

Genome-wide transcriptional changes triggered by water deficit on a drought-tolerant common bean cultivar

“…S6) by drought stress is in agreement with several studies. For instance, a drought-tolerant common bean known as PHB-0683 has been found to change the expression of the cell wall or extracellular proteins in response to water-stress, suggesting that drought caused important changes in the cell wall structure in the common bean plant [ 68 ]. Another drought-tolerant common bean variety, known as BAT 477, has also been analyzed at the transcriptional level under drought conditions [ 69 ].…”