Corrigendum: Allelic haplotype combinations at the MS-P1 region, including P-class pentatricopeptide repeat family genes, influence wide phenotypic variation in pollen grain number through a cytoplasmic male sterility model in citrus.

[This corrects the article DOI: 10.3389/fpls.2023.1163358.].

Allelic haplotype combinations at the MS-P1 region, including P-class pentatricopeptide repeat family genes, influence wide phenotypic variation in pollen grain number through a cytoplasmic male sterility model in citrus.

In citrus breeding programs, male sterility is an important trait for developing seedless varieties. Sterility associated with the male sterile cytoplasm of Kishu mandarin (Kishu-cytoplasm) has been proposed to fit the cytoplasmic male sterility (CMS) model. However, it remains undetermined whether CMS in citrus is controlled by interactions between sterile cytoplasm and nuclear restorer-of-fertility (Rf) genes. Accordingly, mechanisms underlying the control of the wide phenotypic variation in pollen number for breeding germplasm should be elucidated. This study aimed to identify complete linkage DNA markers responsible for male sterility at the MS-P1 region based on fine mapping. Two P-class pentatricopeptide repeat (PPR) family genes were identified as candidates for Rf based on predicted mitochondrial localization and higher expression in a male fertile variety/selected strain than in a male sterile variety. Eleven haplotypes (HT1-HT11) at the MS-P1 region were defined based on genotyping of DNA markers. Association analysis of diplotypes at the MS-P1 region and the number of pollen grains per anther (NPG) in breeding germplasms harboring Kishu-cytoplasm revealed that the diplotypes in this region influenced NPG. Among these haplotypes, HT1 is a non-functional restorer-of-fertility (rf) haplotype; HT2, a less-functional Rf; HT3-HT5 are semi-functional Rfs; and HT6 and HT7 are functional Rfs. However, the rare haplotypes HT8-HT11 could not be characterized. Therefore, P-class PPR family genes in the MS-P1 region may constitute the nuclear Rf genes within the CMS model, and a combination of the seven haplotypes could contribute to phenotypic variation in the NPG of breeding germplasms. These findings reveal the genomic mechanisms of CMS in citrus and will contribute to seedless citrus breeding programs by selecting candidate seedless seedlings using the DNA markers at the MS-P1 region.

Dissecting Breeders' Sense via Explainable Machine Learning Approach: Application to Fruit Peelability and Hardness in Citrus.

"Genomics-assisted breeding", which utilizes genomics-based methods, e.g., genome-wide association study (GWAS) and genomic selection (GS), has been attracting attention, especially in the field of fruit breeding. Low-cost genotyping technologies that support genome-assisted breeding have already been established. However, efficient collection of large amounts of high-quality phenotypic data is essential for the success of such breeding. Most of the fruit quality traits have been sensorily and visually evaluated by professional breeders. However, the fruit morphological features that serve as the basis for such sensory and visual judgments are unclear. This makes it difficult to collect efficient phenotypic data on fruit quality traits using image analysis. In this study, we developed a method to automatically measure the morphological features of citrus fruits by the image analysis of cross-sectional images of citrus fruits. We applied explainable machine learning methods and Bayesian networks to determine the relationship between fruit morphological features and two sensorily evaluated fruit quality traits: easiness of peeling (Peeling) and fruit hardness (FruH). In each of all the methods applied in this study, the degradation area of the central core of the fruit was significantly and directly associated with both Peeling and FruH, while the seed area was significantly and directly related to FruH alone. The degradation area of albedo and the area of flavedo were also significantly and directly related to Peeling and FruH, respectively, except in one or two methods. These results suggest that an approach that combines explainable machine learning methods, Bayesian networks, and image analysis can be effective in dissecting the experienced sense of a breeder. In breeding programs, collecting fruit images and efficiently measuring and documenting fruit morphological features that are related to fruit quality traits may increase the size of data for the analysis and improvement of the accuracy of GWAS and GS on the quality traits of the citrus fruits.

QTL mapping of male sterility and transmission pattern in progeny of Satsuma mandarin.

Seedlessness is one of the important traits in citrus breeding. Male sterility derived from Satsuma mandarin (Citrus unshiu) has been used in Japanese citrus breeding programs to obtain seedless cultivars. The efficiency of seedless cultivar breeding would be improved by developing a selection marker linked to seedlessness. In this study, we performed QTL mapping in 'Okitsu No. 46' × 'Okitsu No. 56' (O46-O56) crosses for the number of pollen grains per anther (NPG) and apparent pollen fertility (APF), two traits used as an index of male sterility, and detected a candidate QTL for NPG (MS-P1) on linkage group 8 with a significant LOD score (7.31) and 47% of variance explained. The QTL for APF (MS-F1) was detected on linkage group 6 with a significant LOD score (5.71) and 63.6% of variance explained. The role of both MS-P1 in reducing NPG and MS-F1 in decreasing APF were confirmed with the 'Okitsu No.46' × 'Kara' (O46-K) cross. Pedigree analysis inferred that both MS-P1 and MS-F1 in 'Okitsu No. 46' were derived from kunenbo (Citrus nobilis) through hassaku (C. hassaku) and 'Sweet Spring'. Cytoplasm analysis revealed that both male-sterile 'Sweet Spring' and 'Okitsu No. 46' have cytoplasm derived from Kishu (C. kinokuni hort. ex Tanaka), but the cytoplasm of male-sterile kunenbo and hassaku were derived from other varieties rather than Kishu. These results suggest that MS-P1 and MS-F1 primarily reduce the NPG and decrease APF, but their expression requires a cytoplasm derived from Kishu. These findings will improve our understanding of the molecular mechanism of male sterility in citrus and help to develop a DNA marker for seedless breeding in citrus.

Genome-wide association study and genomic prediction in citrus: Potential of genomics-assisted breeding for fruit quality traits.

Novel genomics-based approaches such as genome-wide association studies (GWAS) and genomic selection (GS) are expected to be useful in fruit tree breeding, which requires much time from the cross to the release of a cultivar because of the long generation time. In this study, a citrus parental population (111 varieties) and a breeding population (676 individuals from 35 full-sib families) were genotyped for 1,841 single nucleotide polymorphisms (SNPs) and phenotyped for 17 fruit quality traits. GWAS power and prediction accuracy were increased by combining the parental and breeding populations. A multi-kernel model considering both additive and dominance effects improved prediction accuracy for acidity and juiciness, implying that the effects of both types are important for these traits. Genomic best linear unbiased prediction (GBLUP) with linear ridge kernel regression (RR) was more robust and accurate than GBLUP with non-linear Gaussian kernel regression (GAUSS) in the tails of the phenotypic distribution. The results of this study suggest that both GWAS and GS are effective for genetic improvement of citrus fruit traits. Furthermore, the data collected from breeding populations are beneficial for increasing the detection power of GWAS and the prediction accuracy of GS.

Segregation and Heritability of Male Sterility in Populations Derived from Progeny of Satsuma Mandarin.

Male sterility derived from Satsuma mandarin (Citrus unshiu) has been used in Japanese citrus breeding programs to obtain seedless cultivars, which is a desirable trait for consumers. Male sterility has often been evaluated by anther development or pollen fertility; however, the inheritance and heritability of male sterility derived from Satsuma is poorly understood. In this study, we investigated the mode of inheritance and broad-sense heritability of male sterility derived from Satsuma. Initially, we evaluated the total number of pollen grains per anther and apparent pollen fertility, as indicated by lactophenol blue staining, in 15 citrus cultivars and selections to understand the male sterility of Satsuma. The results indicated that male sterility was primarily caused by decreased number of pollen grains per anther in progeny of Satsuma. We also evaluated these traits in three F1 populations (hyuganatsu × 'Okitsu No. 56', 'Okitsu No. 46' × 'Okitsu No. 56' and 'Okitsu No. 46' × 'Kara'), of which the parents are derived from Satsuma. Individuals in these populations showed strong segregation for number of pollen grains per anther. The apparent fertility of pollen also showed segregation but was almost constant at 70%-90%. The estimated broad-sense heritability for the number of pollen grains per anther was as high as 0.898 in the 'Okitsu No. 46' × 'Okitsu No. 56' and 'Okitsu No. 46' × 'Kara' populations. These results indicated that the number of pollen grains per anther primarily determined male sterility among progeny of Satsuma, and this trait was inherited by the progeny. Development of DNA markers closely linked to male sterility using the F1 populations of 'Okitsu No. 46' × 'Okitsu No. 56' and 'Okitsu No. 46' × 'Kara' is expected to contribute to the breeding of novel seedless citrus cultivars.

Regulation of human autoimmune regulator (AIRE) gene translation by miR-220b.

Although mutations of autoimmune regulator (AIRE) gene are responsible for autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), presenting a wide spectrum of many characteristic and non-characteristic clinical features, some patients lack AIRE gene mutations. Therefore, something other than a mutation, such as dysregulation of AIRE gene, may be a causal factor for APECED or its related diseases. However, regulatory mechanisms for AIRE gene expression and/or translation have still remained elusive. We found that IL-2-stimulated CD4(+) T (IL-2T) cells showed a high expression of AIRE gene, but very low AIRE protein production, while Epstein-Barr virus-transformed B (EBV-B) cells express both AIRE gene and AIRE protein. By using microarray analysis, we could identify miR-220b as a possible regulatory mechanism for AIRE gene translation in IL-2T cells. Here we report that miR-220b significantly reduced the expression of AIRE protein in AIRE gene with 3'UTR region transfected 293T cells, whereas no alteration of AIRE protein production was observed in the open reading frame of AIRE gene alone transfected cells. In addition, anti-miR-220b reversed the inhibitory function of miR-220b for the expression of AIRE protein in AIRE gene with 3'UTR region transfected cells. Moreover, when AIRE gene transfected cells with mutated 3'UTR were transfected with miR-220b, no reduction of AIRE protein production was observed. Taken together, it was concluded that miR-220b inhibited the AIRE gene translation through the 3'UTR region of AIRE gene, indicating that miR-220b could serve as a regulator for human AIRE gene translation.

Preventive effect of N-acetylcysteine on contrast-induced nephropathy following coronary angiography and angioplasty.

Contrast-induced nephropathy (CIN) is one of the serious side effects of contrast media. A few studies have suggested that N-acetylcysteine (NAC) is effective to prevent CIN, but the efficacy remains unclear in Japanese. Therefore, we retrospectively studied the preventive effect of NAC on CIN in Sakakibara Heart Institute. Patients who had been administered NAC for the purpose of preventing CIN before coronary intervention between February 2005 and November 2006 were included in the NAC group. In addition, age- and rate of diabetes mellitus-matched controls were randomly extracted. We retrieved and analyzed patient data including demographics, NAC dosage, and serum creatinine concentrations (Scr). NAC group (n=16) showed significantly higher baseline Scr (p<0.01) and a tendency toward a lower dose of contrast media (p=0.068) compared with controls (n=48). Since the occurrence of CIN was low, there was no significant difference in the proportion of CIN between the groups (NAC: 6%, controls: 4%). NAC group trended toward a decrease in Scr after the use of contrast media, while controls increased (-0.04+/-0.25 versus +0.03+/-0.36 mg/dl, p=0.096). The multivariate analysis showed that the dosage of NAC is inversely correlated with Scr independent of baseline Scr and dosage of contrast media. Despite higher baseline Scr (i.e., high-risk with CIN) in the NAC group, the real Scr value reflected a lower trend on average. In addition, this finding suggests that a larger dose of NAC results in a lower Scr value, we consider that the NAC dosage more likely prevented CIN.

A convenient synthesis of 1,1-disubstituted 1,2,3,4-tetrahydroisoquinolines via Pictet-Spengler reaction using titanium(IV) isopropoxide and acetic-formic anhydride.

A synthesis of 1,1-disubstituted 1,2,3,4-tetrahydroisoquinolines (6) was achieved in a highly efficient manner via Pictet-Spengler reaction of arylethylamines (1) and acyclic and cyclic ketones (2) using titanium (IV) isopropoxide and acetic-formic anhydride. The cyclization of the in situ formed acyliminium ion (4) to N-formyl 1,2,3,4-tetrahydroisoquinoline (5) was greatly facilitated by using trifluoroacetic acid as an additional reagent. The Pictet-Spengler reaction was carried out by one pot procedure, providing a convenient and effective method for preparing various 1,2,3,4-tetrahydroisoquinolines.

[Outcome of neonatal screening for hearing loss in neonatal intensive care unit and well-born nursery infants].

A newborn hearing screening was conducted on 319 neonatal intensive care unit (NICU) and 1200 well-born nursery (WBN) infants. Mean NICU birth weight was 1997 g and mean gestational age 34 weeks. Auditory brainstem response was studied in screening in NICU infants. Otoacoustic emission (OAE) or automated auditory brainstem response (AABR) was used in primary WBN screening. All infants not bilaterally passing hearing screening before discharge were recalled for outpatient retesting. If the outcome was still failure, ABR screening was conducted. The prevalence of infants diagnosed with hearing loss was 1.1% (16 of 1519). Of these 16, 75% were from the NICU and 75% were at risk for hearing loss. Mean age at hearing loss identification was 12.9 weeks in the WBN and mean age at hearing aid fitting was 16.1 weeks. Mean age at hearing aid fitting was lower for WBN than for NICU infants. Hearing loss identification and hearing aid fitting are thus feasible in NICU and WBN infants in universal newborn hearing screening.