Arabidopsis ALF5, a multidrug efflux transporter gene family member, confers resistance to toxins

From Flavanols Biosynthesis to Wine Tannins: What Place for Grape Seeds?

Phenolic compounds are among the most important quality factors of wines. They contribute to the organoleptic characteristics of wine such as color, astringency, and bitterness. Although tannins found in wine can come from microbial and oak sources, the main sources of polyphenols are grape skins and seeds. Since the 1960s, this subject has been widely studied by a large number of researchers covering different types of wine, climate conditions, growing practices, and grape varieties. As these works have been conducted under different conditions, the data collected can be conflicting. Moreover, even though the biosynthesis of the major proanthocyanidins units (+)-catechin and (-)-epicatechin is well-known, the mechanism of their polymerization remains unexplained. This is why the question remains: what factors influence the biosynthesis, the quantity, and the distribution of tannins in grape seeds and how can winemaking processes impact the extractability of seed tannins in wine?

Transcriptome-wide characterization and functional analysis of MATE transporters in response to aluminum toxicity in Medicago sativa L

Multidrug and toxic compound extrusion (MATE) transporters contribute to multidrug resistance and play major determinants of aluminum (Al) tolerance in plants. Alfalfa (Medicago sativa L.) is the most extensively cultivated forage crop in the world, yet most alfalfa cultivars are not Al tolerant. The basic knowledge of the MATE transcripts family and the characterisation of specific MATE members involved in alfalfa Al stress remain unclear. In this study, 88 alfalfa MATE (MsMATE) transporters were identified at the whole transcriptome level. Phylogenetic analysis classified them into four subfamilies comprising 11 subgroups. Generally, five kinds of motifs were found in group G1, and most were located at the N-terminus, which might confer these genes with Al detoxification functions. Furthermore, 10 putative Al detoxification-related MsMATE genes were identified and the expression of five genes was significantly increased after Al treatment, indicating that these genes might play important roles in conferring Al tolerance to alfalfa. Considering the limited functional understanding of MATE transcripts in alfalfa, our findings will be valuable for the functional investigation and application of this family in alfalfa.

Genes Involved in Stress Response and Especially in Phytoalexin Biosynthesis Are Upregulated in Four Malus Genotypes in Response to Apple Replant Disease

Apple replant disease (ARD) is a soil-borne disease, which is of particular importance for fruit tree nurseries and fruit growers. The disease manifests by a poor vegetative development, stunted growth, and reduced yield in terms of quantity and quality, if apple plants (usually rootstocks) are replanted several times at the same site. Genotype-specific differences in the reaction of apple plants to ARD are documented, but less is known about the genetic mechanisms behind this symptomatology. Recent transcriptome analyses resulted in a number of candidate genes possibly involved in the plant response. In the present study, the expression of 108 selected candidate genes was investigated in root and leaf tissue of four different apple genotypes grown in untreated ARD soil and ARD soil disinfected by γ-irradiation originating from two different sites in Germany. Thirty-nine out of the 108 candidate genes were differentially expressed in roots by taking a p-value of < 0.05 and a fold change of > 1.5 as cutoff. Sixteen genes were more than 4.5-fold upregulated in roots of plants grown in ARD soil. The four genes MNL2 (putative mannosidase); ALF5 (multi antimicrobial extrusion protein); UGT73B4 (uridine diphosphate (UDP)-glycosyltransferase 73B4), and ECHI (chitin-binding) were significantly upregulated in roots. These genes seem to be related to the host plant response to ARD, although they have never been described in this context before. Six of the highly upregulated genes belong to the phytoalexin biosynthesis pathway. Their genotype-specific gene expression pattern was consistent with the phytoalexin content measured in roots. The biphenyl synthase (BIS) genes were found to be useful as early biomarkers for ARD, because their expression pattern correlated well with the phenotypic reaction of the Malus genotypes investigated.