The mitochondrial malate dehydrogenase 1 gene GhmMDH1 is involved in plant and root growth under phosphorus deficiency conditions in cotton

Abstract

Cotton, an important commercial crop, is cultivated for its natural fibers, and requires an adequate supply of soil nutrients, including phosphorus, for its growth. Soil phosporus exists primarily in insoluble forms. We isolated a mitochondrial malate dehydrogenase (MDH) gene, designated as GhmMDH1, from Gossypium hirsutum L. to assess its effect in enhancing P availability and absorption. An enzyme kinetic assay showed that the recombinant GhmMDH1 possesses the capacity to catalyze the interconversion of oxaloacetate and malate. The malate contents in the roots, leaves and root exudates was significantly higher in GhmMDH1-overexpressing plants and lower in knockdown plants compared with the wild-type control. Knockdown of GhmMDH1 gene resulted in increased respiration rate and reduced biomass whilst overexpression of GhmMDH1 gave rise to decreased respiration rate and higher biomass in the transgenic plants. When cultured in medium containing only insoluble phosphorus, Al-phosphorus, Fe-phosphorus, or Ca-phosphorus, GhmMDH1-overexpressing plants produced significantly longer roots and had a higher biomass and P content than WT plants, however, knockdown plants showed the opposite results for these traits. Collectively, our results show that GhmMDH1 is involved in plant and root growth under phosphorus deficiency conditions in cotton, owing to its functions in leaf respiration and P acquisition.

Comparative Genome-Wide Analysis of the Malate Dehydrogenase Gene Families in Cotton

“…Among these subgroups, mitochondrial MDHs and cytosolic MDHs are two major groups. Recently, the subcellular location of mitochondrial MDH (GhmMDH1) has been determined by Wang et al [9], meanwhile we have confirmed the subcellular location of cytosolic MDH in the cytosol during the functional characterization of a cotton cytosolic malate dehydrogenase (GhcMDH1) gene (unpublished data). Whereas, the subcellular locations of other orthologues from peroxisomal MDH (AtpMDH1), plastidal MDH (AtpdMDH) and chloroplastic MDH (BrachMDH) have also been confirmed in several functional studies reported by Pracharoenwattana et al [64], Selinski et al [65] and Li et al [66], respectively.…”

“…For example, GhmMDH1 and GhcMDH1 from the mitochondrial MDH and cytoplasmic MDH subgroups, respectively, were highly expressed in vegetative tissues and at different developmental stages of fiber, suggesting that they might play an important function in cotton growth and fiber development. Similarly, Wang et al (2015) reported that GhmMDH1 -overexpressing plants had a significantly elevated MDH activity and malate content, whereas RNAi plants showed a lower activity and malate level compared to those of with wild-type plants [9]. In Arabidopsis , the MDH genes with decrease leaf respiration and altered photorespiration are located in the mitochondria [6].…”

“…Whereas, when cotton is cultured in medium containing only insoluble phosphorus, Ca-phosphorus, or Al-phosphorus, GhmMDH1 overexpressing plant produced significantly higher biomass and had a longer root and Phosphorus content than wild type plants, however, knockdown plant showed the opposite results [9]. Interestingly, in the promoter region of allotetraploid cotton MDH genes, we found that 38 and 33 genes possessed an average of 1.60 and 1.40 copies per gene for adverse environmental stimulus, such as defense and heat stress responsive elements, respectively (S6 Table and Fig 6).…”

“…Based on gene organization and protein sequence similarity, different MDHs have different reaction requirements, malate selectivities and subcellular localizations [4]. To date, abundant MDH genes have been characterized from several plant species, including wheat [5], Arabidopsis [6], maize [7], apple [8] and cotton [9]. Among these MDH genes, the mitochondrial and cytosolic MDH genes are the most frequently investigated, likely because of their abundance in the plant kingdom.…”

“…An increasing number of studies indicate that MDHs and their catalytic product malate are involved in several processes of plant growth and development, e.g., root growth [10], seed development [11], and leaf respiration [6]. MDHs also play crucial roles in various biotic and abiotic stresses, such as pathogen [12], nutrient [9], salt and cold [8] stresses.…”