PtxtPME1 and homogalacturonans influence xylem hydraulic properties in poplar.

While the xylem hydraulic properties, such as vulnerability to cavitation (VC), are of paramount importance in drought resistance, their genetic determinants remain unexplored. There is evidence that pectins and their methylation pattern are involved, but the detail of their involvement and the corresponding genes need to be clarified. We analyzed the hydraulic properties of the 35S::PME1 transgenic aspen that ectopically under- or over-express a xylem-abundant pectin methyl esterase, PtxtPME1. We also produced and analyzed 4CL1::PGII transgenic poplars expressing a fungal polygalacturonase, AnPGII, under the control of the Ptxa4CL1 promoter that is active in the developing xylem after xylem cell expansion. Both the 35S::PME1 under- and over-expressing aspen lines developed xylem with lower-specific hydraulic conductivity and lower VC, while the 4CL1::PGII plants developed xylem with a higher VC. These xylem hydraulic changes were associated with modifications in xylem structure or in intervessel pit structure that can result in changes in mechanical behavior of the pit membrane. This study shows that homogalacturonans and their methylation pattern influence xylem hydraulic properties, through its effect on xylem cell expansion and on intervessel pit properties and it show a role for PtxtPME1 in the xylem hydraulic properties.

Insights into xylem vulnerability to cavitation in Fagus sylvatica L.: phenotypic and environmental sources of variability.

Xylem vulnerability to cavitation is a key parameter in understanding drought resistance of trees. We determined the xylem water pressure causing 50% loss of hydraulic conductivity (P(50)), a proxy of vulnerability to cavitation, and we evaluated the variability of this trait at tree and population levels for Fagus sylvatica. We checked for the effects of light on vulnerability to cavitation of stem segments together with a time series variation of P(50). Full sunlight-exposed stem segments were less vulnerable to cavitation than shade-exposed ones. We found no clear seasonal change of P(50), suggesting that this trait was designed for a restricted period. P(50) varied for populations settled along a latitudinal gradient, but not for those sampled along an altitudinal gradient. Moreover, mountainside exposure seemed to play a major role in the vulnerability to cavitation of beech populations, as we observed the differences along north-facing sides but not on south-facing sides. Unexpectedly, both north-facing mountainside and northern populations appeared less vulnerable than those grown on the southern mountainside or in the South of France. These results on beech populations were discussed with respect to the results at within-tree level.

Poplar vulnerability to xylem cavitation acclimates to drier soil conditions.

Xylem vulnerability to cavitation differs between tree species according to their drought resistance, more xerophilous species being more resistant to xylem cavitation. Variability in xylem vulnerability to cavitation is also found within species, especially between in situ populations. The origin of this variability has not been clearly identified. Here we analyzed the response of xylem hydraulic traits of Populus tremula x Populus alba trees to three different soil water regimes. Stem xylem vulnerability was scored as the xylem water potential causing 12, 50 and 88% loss of conductivity (P(12), P(50) and P(88)). Vulnerability to cavitation was found to acclimate to growing conditions under different levels of soil water content, with P(50) values of -1.82, -2.03 and -2.45 MPa in well-watered, moderately water-stressed and severely water-stressed poplars, respectively. The value of P(12), the xylem tension at which cavitation begins, was correlated with the lowest value of midday leaf water potential (psi m) experienced by each plant, the difference between the two parameters being approximately 0.5 MPa, consistent with the absence of any difference in embolism level between the different water treatments. These results support the hypothesis that vulnerability to cavitation is a critical trait for resistance to drought. The decrease in vulnerability to cavitation under growing conditions of soil drought was correlated with decreased vessel diameter, increased vessel wall thickness and a stronger bordered pit field (t/b)(2). The links between these parameters are discussed.

Seminal plasma anti-Müllerian hormone level correlates with semen parameters but does not predict success of testicular sperm extraction (TESE).

AIM: To assess seminal plasma anti-Müllerian hormone (AMH) level relationships in fertile and infertile males. METHODS: Eighty-four male cases were studied and divided into four groups: fertile normozoospermia (n = 16), oligoasthenoteratozoospermia (n = 15), obstructive azoospermia (OA) (n = 13) and non-obstructive azoospermia (NOA) (n = 40). Conventional semen analysis was done for all cases. Testicular biopsy was done with histopathology and fresh tissue examination for testicular sperm extraction (TESE) in NOA cases. NOA group was subdivided according to TESE results into unsuccessful TESE (n = 19) and successful TESE (n = 21). Seminal plasma AMH was estimated by enzyme linked immunosorbent assay (ELISA) and serum follicular stimulating hormone (FSH) was estimated in NOA cases only by radioimmunoassay (RIA). RESULTS: Mean seminal AMH was significantly higher in fertile group than in oligoasthenoteratozoospermia with significance (41.5 +/- 10.9 pmol/L vs. 30.5 +/- 10.3 pmol/L, P < 0.05). Seminal AMH was not detected in any OA patients. Seminal AMH was correlated positively with testicular volume (r = 0.329, P = 0.005), sperm count (r = 0.483, P = 0.007), sperm motility percent (r = 0.419, P = 0.021) and negatively with sperm abnormal forms percent (r = -0.413, P = 0.023). Nonsignificant correlation was evident with age (r = -0.155, P = 0.414) and plasma FSH (r = -0.014, P = 0.943). In NOA cases, seminal AMH was detectable in 23/40 cases, 14 of them were successful TESE (57.5%) and was undetectable in 17/40 cases, 10 of them were unsuccessful TESE (58.2%). CONCLUSION: Seminal plasma AMH is an absolute testicular marker being absent in all OA cases. However, seminal AMH has a poor predictability for successful testicular sperm retrieval in NOA cases.