Triterpenoids in aerenchymatous phellem contribute to internal root aeration and waterlogging adaptability in soybeans.

Soybeans (Glycine max) develop newly differentiated aerenchymatous phellem (AP) in response to waterlogging stress. AP is formed in the hypocotyl and root, thus contributing to internal aeration and adaptation to waterlogging for several legumes. Extensive accumulation of triterpenoids - lupeol and betulinic acid - has been identified in AP. However, their physiological roles in plants remain unclarified. Lupeol is converted from 2,3-oxidosqualene by lupeol synthase (LUS) and oxidized to betulinic acid. Notably, soybeans have two LUS genes (GmLUS1 and GmLUS2). Functional analysis was performed to reveal the biological and physiological functions of triterpenoids in AP using lus mutants. The AP cells of lus1 mutant lacked triterpenoid accumulation and epicuticular wax. Lupeol and betulinic acid were the major components of epicuticular wax and contributed to tissue hydrophobicity and oxygen transport to the roots. Tissue porosity in AP was lower in the lus1 mutant than in the wild-type, which resulted in reduced oxygen transport to the roots via AP. This reduction in oxygen transport resulted in shallow root systems under waterlogged conditions. Triterpenoid accumulation in AP contributes to effective internal aeration and root development for adaptation to waterlogging, suggesting the significance of triterpenoids in improving waterlogging tolerance.

Risk Factors for Lymph Node Metastasis and Recurrence in T1 Colorectal Cancer: Analysis of 801 Patients in a Single Institute.

OBJECTIVE: To identify risk factors for lymph node metastasis and postoperative recurrence of pT1 colorectal cancer by clinicopathological study of surgically resected cases. METHODS: In 801 patients with pT1 colorectal cancer who underwent surgical resection with lymph node dissection between April 2007 and January 2021, we evaluated clinicopathological factors (age, gender, BMI, serum CEA level, tumor localization, additional resection after endoscopic treatment, operation time, blood loss, histological type, tumor size, vascular invasion, and central lymph node dissection). We performed univariate and multivariate analyses to examine risk factors for lymph node metastasis. We also examined risk factors for recurrence in 583 patients up to December 2017. RESULTS: Lymph node metastasis was observed in 100/801 patients (12.5%). Multivariate analysis of lymph node metastasis showed that patients with positive lymphatic invasion (odds ratio 2.57, 95% CI 1.62-4.04, P < .0001), positive venous invasion (odds ratio 2.31, 95% CI 1.48-3.61, P = .0002), and histologically poorly differentiated type (odds ratio 4.54, 95% CI 1.35-15.2, P = .014) were identified as risk factors. Postoperative recurrence was observed in 18/580 patients (3.1%). Risk factors for postoperative recurrence were also examined, including preoperative endoscopic treatment (odds ratio 3.59, 95% CI 1.18-10.9, P = .024), positive venous invasion (odds ratio 3.63, 95% CI 1.22-10.8, P = .021), positive lymph node metastasis (odds ratio 4.91, 95% CI 1.10-21.8, P = .037) were extracted as risk factors. DISCUSSION: In this study, venous invasion, lymphatic invasion, and histologically poorly differentiated type were identified as risk factors for lymph node metastasis in T1 colorectal cancer, and positive venous invasion, positive lymph node metastasis, and preoperative endoscopic treatment were identified as risk factors for recurrence. We hope that large prospective study will lead to the development of a more specific treatment strategy, including endoscopic treatment and additional surgical resection.

Short-term results of robot-assisted colorectal cancer surgery using Senhance Digital Laparoscopy System.

BACKGROUND: The Senhance Digital Laparoscopy System (Asensus Surgical Inc, Morrisville, NC, United States), which was introduced for the first time in Japan by our hospital, is a new surgical assistive robot following the da Vinci Surgical System. We herein report the short-term outcomes of 55 colorectal cancer surgery cases using this system at our hospital to assess the feasibility and safety of our procedures. MATERIALS AND METHODS: We retrospectively reviewed the patient backgrounds and surgical outcomes of 55 patients who underwent Senhance-assisted laparoscopic colorectal cancer surgery. RESULTS: The median age was 71 years. There were 31 males and 24 females, and the median body mass index was 23.1 kg/m2 . Fifteen patients had a history of abdominal surgery. The most common surgical technique was ileocecal resection (18 cases, 32.7%), followed by high anterior resection (11 cases, 20.0%). D2 or D3 dissection was performed in each operation, and D3 dissection was performed in 41 cases (74.5%). The median operative time was 240 minutes, the median blood loss was 5 mL, there were no intraoperative complications, and there were no cases of intraoperative blood transfusion. The median postoperative hospital stay was 7 days, which was comparable to conventional laparoscopic surgery. Postoperative complications of grade 2 or higher in the Clavien-Dindo classification were observed in two cases. CONCLUSION: The short-term results of 55 colorectal cancer surgery cases using the Senhance Digital Laparoscopy System were excellent and the system was introduced and surgery was safely performed.

[Retrospective Analysis of Treatment Strategies for Local Recurrence following Radical Resection of Rectal Cancer].

We report the findings from a retrospective study to determine the optimum treatment strategy for local recurrence following radical resection of rectal cancer. In our department, among all 430 patients that underwent radical resection of rectal cancer from 2012 to 2018, there were 28 patients that developed local recurrence. Of those patients, 12 underwent surgical treatment(Op group)and 16 did not(N-Op group). In the Op group, 8 patients underwent radical resection, of which 2 patients remained recurrence-free, and the other 6 patients developed recurrence. In the N-Op group, 6 patients were treated with systemic chemotherapy alone, a further 6 patients had palliative irradiation in addition to systemic chemotherapy, and the other 4 selected best supportive care(2 patients were treated with palliative irradiation). In the 8 patients who had palliative irradiation, 7 showed a decrease in numerical rating scale(NRS)after irradiation. The adverse events of palliative irradiation were scrotal dermatitis in 1 patient and perianal inflammation in another 3 patients. Our surgical results for local recurrence of rectal cancer in our department were worse in terms of recurrence rate, so these findings suggest that the preoperative surgical strategy could be reviewed, as well as the actual surgical methods such as the optimal circumferential resection margin. Palliative irradiation was found to be useful for pain control. However, the occurrence of adverse events remains a concern.

The first single-incision plus one-port transverse colon resection using Senhance Digital Laparoscopy System: a case report.

BACKGROUND: We have introduced the Senhance Digital Laparoscopy System and actively use for colorectal cancer surgery. Recently, we also try to perform surgery by reduce port as less invasive method. For the first time, we report a case of single-incision plus one-port transverse colectomy using Senhance system. CASE PRESENTATION: The case was a 57-year-old woman, diagnosed with transverse colon cancer referred to our department. The preoperative diagnosis was cT1bN0M0, Stage I. We performed single-incision plus one-port transverse colon resection using Senhance system without any problems. The operative time was 203 min and the blood loss was 35 ml. CONCLUSION: We report the first case of single-incision plus one-port transverse colectomy using Senhance system. We trust this approach will find increasing use, enabling a safer means of minimally invasive robotic surgery.

Impact of Lymphovascular Invasion in Patients With Stage II Colorectal Cancer: A Propensity Score-matched Study.

BACKGROUND/AIM: Whether lymphovascular invasion (LVI) is a high-degree risk factor in stage II colorectal cancer has not been fully clarified, as different results have been reported in the literature. If LVI is a risk factor, postoperative chemotherapy may be recommended. The purpose of this study was to evaluate the impact of lymphovascular invasion on disease recurrence and patient prognosis in conjunction with stage II colorectal cancer (CRC). PATIENTS AND METHODS: A total of 636 patients with stage II CRC, each undergoing radical resection between April 2007 and December 2015, were selected for the study. Subjects with or without venous or lymphatic invasion were assigned to positive and negative groups, respectively. We then compared overall survival (OS) and disease-free survival (DFS) using propensity score matching. RESULTS: After matching (n=226, each group), OS and DFS were found to be significantly lower (OS: p=0.047; DFS: p=0.004) in patients positive (vs. negative) for venous invasion. However, the same was not true of lymphatic invasion. After matching, positive and negative groups (n=92, each) did not significantly differ in terms of OS (p=0.951) or DFS (p=0.258). CONCLUSION: In patients with stage II CRC, venous invasion proved to be a significant high-degree risk factor that may warrant adjuvant chemotherapy.

Prognostic Utility of Geriatric Nutritional Risk Index After Curative Resection of Colorectal Cancer: A Propensity Score-matched Study.

Background/Aim: The geriatric nutrition risk index (GNRI) is a presumptive prognosticator in a variety of carcinomas. We investigated whether it similarly predicts outcomes of elderly patients with colorectal cancer (CRC). Patients and Methods: A total of 904 older adults (≥65 years) undergoing radical resections of CRC between April 2011 and December 2015 proved eligible for study. Each was grouped by preoperative status (cut-off point, 98) as low-level or normal GNRI, using propensity score matching to compare rates of complications, disease-free survival (DFS), and overall survival (OS). Results: After matching (n=127, each group), those with low-level (vs. normal) GNRI values experienced significantly more complications (p=0.001), and 5-year survival was significantly poorer (DFS: p=0.006; OS: p=0.002). Conclusion: In elderly patients with resected CRC, preoperative GNRI may have significant prognostic merit.

Right hemicolectomy with D3 lymph node dissection for right-sided transverse colon cancer using the Senhance robotic system: a case report.

BACKGROUND: The evolution of remote systems and artificial intelligence technology has led to increase in robotic surgeries. One system used in this case report is the Senhance robotic system. The most important premise for using robotic surgery in cancer therapeutics is to ensure oncological safety. Similar to conventional laparoscopic surgery, robotic surgery needs to be a reliable and secure surgical procedure, such as complete mesocolic excisions with central vascular ligations in Western countries or D3 lymph node dissections (dissection of the lymph nodes that locates from the origin to the terminal branch of the main feeding artery of cancer) in Japan. CASE PRESENTATION: A 76-year-old man underwent clinical examination for severe anemia. He was diagnosed with transverse colon cancer of tumor (T)3, node (N)1a, metastasis (M)0 cancer stage IIIA. A right hemicolectomy with D3 lymph node dissection using the Senhance surgical system was performed. The operative time was 313 min and the estimated blood loss was 5 ml. He was discharged from our hospital 12 days after the surgery without any complications. What is the remarkable of this report, not only mobilization of right colon but also D3 lymph node dissection and vascular ligation were performed intraperitoneally by using Senhance robotic system as conventional laparoscopic surgery. We tried using fourth robotic arm to accomplish lymphadenectomies and middle colic artery dissection. A right hemicolectomy with D3 dissection using the Da Vinci surgical system was reported. Another report of a right hemicolectomy performed with the Senhance robotic system was identified; however, in that study, lymph node dissections were not performed intraperitoneally. CONCLUSIONS: Therefore, to our knowledge, this is the first report using the Senhance robotic system for right hemicolectomy with D3 dissection. We hope that our case report will assist in the establishment of this robotic procedure in surgical practice.

A rare case of symptomatic grossly-visible biliary intraepithelial neoplasia mimicking cholangiocarcinoma.

BACKGROUND: Biliary intraepithelial neoplasia (BilIN) is often distinguished by what it is not: the precancerous lesions are not mass-forming, are not the cause of bile duct obstruction, and are small enough (less than 5 mm long) to evade detection by the naked eye. Here, we describe an atypical case of BilIN resembling cholangiocarcinoma (CC) that was large enough to be identified by diagnostic imaging and presented with obstructive jaundice caused by a hematoma in the common bile duct (CBD). CASE PRESENTATION: A 64-year-old man presented to our hospital with upper abdominal pain and anorexia. Initial laboratory examinations revealed increased total bilirubin and a computed tomography (CT) scan revealed a dilated CBD. Gastroenterologists performed an endoscopic sphincterotomy (EST), which revealed that the cause of obstructive jaundice was a hematoma in the CBD. Enhanced CT scan and magnetic resonance cholangiopancreatography (MRCP) performed after the hematoma was drained showed improved dilation of the CBD and an enhanced wall thickness of bile duct measuring 25 × 10 mm at the union of the cystic and common hepatic ducts. A cholangioscope detected an elevated tumor covered by sludge in the CBD, and we performed an extrahepatic bile duct resection and cholecystectomy. The postoperative course was uneventful and the pathological examination of the resected tumor revealed that although the ulcerated lesion had inflammatory granulation tissue, it did not contain the components of invasive carcinoma. Many consecutive intraepithelial micropapillary lesions spread around the ulcerated lesion, and the epithelial cells showed an increased nucleus-to-cytoplasm ratio, nuclear hyperchromasia, and architectural atypia. The pathological diagnosis was BilIN-1 to -2. Immunohistochemical staining showed that S100P was slightly expressed and MUC5AC was positive, while MUC1 was negative and p53 was not overexpressed. CONCLUSION: We experienced an atypical case of BilIN mimicking CC that presented with obstructive jaundice caused by a hematoma in the CBD. Our case suggested that the occurrence of BilIN can be triggered by factors other than inflammation, and can grow to a size large enough to be detected by image analyses.

CO2 retention: The key to stopping hiccups.

BACKGROUND: While investigating the mechanisms behind hiccups, our team discovered what could be the sufficient physiological conditions for terminating even persistent cases. METHODS: To investigate the role of CO2 retention, a healthy male volunteer was asked to perform three kinds of rebreathing experiments using different materials: (I) a 20 L air-filled plastic bag, (II) a 20 L air-filled plastic bag with a 1.5 × 1.5 cm hole and (III) a 20 L oxygen-filled plastic bag. During each experiment, CO2 level upon expiration (EtCO2 ) and inspiration (InspCO2 ) were measured until the volunteer gave up. Once the safety of this manoeuvre was demonstrated with the volunteer, we performed the technique using the materials from experiment (I) on two actual patients with persistent hiccups. RESULTS: In experiments (I) and (III), InspCO2 increased from the beginning and reached almost the same level as EtCO2 after 90 seconds. Both levels continued simultaneously increasing, finally reaching 56 mm Hg in (I) and 79 mm Hg in (III), respectively. In (II), both increased; however, after 120 seconds, EtCO2 plateaued at 47 mm Hg and InspCO2 at 37 mm Hg. In the actual patients, both CO2 levels reached the same value of 35.9 mm Hg at 60 seconds and 37.0 mm Hg at 90 seconds, and hiccups stopped at 195 seconds and at 359 seconds when EtCO2 reached 50 mm Hg and 53 mm Hg, respectively. CONCLUSION: The study determined that to successfully obstruct the mechanisms causing hiccups, it is necessary that the level of InspCO2 not only increases at the same level as EtCO2 , but also reaches approximately 50 mm Hg.

Sucrose supply from leaves is required for aerenchymatous phellem formation in hypocotyl of soybean under waterlogged conditions.

Background and Aims: Soil waterlogging often causes oxygen deficiency in the root systems of plants and severely inhibits plant growth. Formation of aerenchyma - interconnected spaces that facilitate the movement of gases between and within the aerial and submerged parts of plants - is an adaptive trait for coping with waterlogged conditions. Soybean (Glycine max) forms porous secondary tissues known as aerenchymatous phellem (AP), which are derived from the outermost cell layer of phellogen. To understand what factors other than waterlogging are involved in phellogen and AP formation, we examined how their formation in soybean seedlings was affected by darkness, CO2 deficiency and blockage of phloem transport. Methods: Aerenchymatous phellem and phellogen formation were expressed as area ratios in cross-sections of hypocotyl. CO2 was depleted by use of calcium oxide and sodium hydroxide. Phloem transport was blocked by heat-girdling of hypocotyls. Sucrose levels were measured by spectrophotometry. Key Results: Under light conditions, waterlogging induced the accumulation of high concentrations of sucrose in hypocotyls, followed by phellogen and AP formation in hypocotyls. Phellogen formation and AP formation were inhibited by darkness, CO2 deficiency and blockage of phloem transport. Phellogen formation and AP formation were also inhibited by excision of shoots above the epicotyl, but they recovered following application of sucrose (but not glucose or fructose application) to the cut surface. Conclusions: The results demonstrate that sucrose derived from leaves is essential for AP and phellogen formation in soybean hypocotyls under waterlogged soil conditions. Maintenance of a high sucrose concentration is thus essential for the development of phellogen and AP and the differentiation of phellogen to AP.

Transfer of the Rsv3 locus from 'Harosoy' for resistance to soybean mosaic virus strains C and D in Japan.

Resistance to soybean mosaic virus (SMV) is imperative for soybean (Glycine max (L.) Merr.) production in the Tohoku region. Molecular markers for SMV resistance were previously reported for U.S. SMV strains, but they cannot be applied because of the differences in strain classification between Japan and the U.S. A U.S. variety 'Harosoy' has been used mainly as a donor of resistance to SMV strains C and D in a Japanese breeding program, resulting in resistant varieties such as 'Fukuibuki.' Because 'Harosoy' harbors the Rsv3 gene conferring resistance to the virulent SMV strain groups, G5 through G7, it appears that the Rsv3 gene confers resistance to strains C and D. In this study, we introduced resistance to the two strains from 'Fukuibuki' into a leading variety 'Ohsuzu' by recurrent backcrossing with marker-assisted selection. All lines selected with markers near Rsv3 showed resistance to the strains, suggesting that the Rsv3 locus is responsible for the resistance. Three years of trials showed that one of the breeding lines, 'Tohoku 169,' was equivalent to 'Ohsuzu' with respect to agricultural characteristics such as seed size, maturity date, and seed yield, except for the SMV resistance.

Laser microdissection-based gene expression analysis in the aleurone layer and starchy endosperm of developing rice caryopses in the early storage phase.

BACKGROUND: Rice endosperm is composed of aleurone cells in the outermost layers and starchy endosperm cells in the inner part. The aleurone layer accumulates lipids, whereas starchy endosperm mainly accumulates starch. During the ripening stage, the starch accumulation rate is known to be asynchronous, depending on the position of the starchy endosperm. Different physiological and molecular mechanisms are hypothesized to underlie the qualitative and quantitative differences in storage products among developing rice endosperm tissues. RESULTS: Target cells in aleurone layers and starchy endosperm were isolated by laser microdissection (LM), and RNAs were extracted from each endosperm tissue in the early storage phase. Genes important for carbohydrate metabolism in developing endosperm were analyzed using qRT-PCR, and some of the genes showed specific localization in either tissue of the endosperm. Aleurone layer-specific gene expression of a sucrose transporter, OsSUT1, suggested that the gene functions in sucrose uptake into aleurone cells. The expression levels of ADP-glucose pyrophosphorylase (AGPL2 and AGPS2b) in each endosperm tissue spatially corresponded to the distribution of starch granules differentially observed among endosperm tissues. By contrast, expressions of genes for sucrose cleavage-hexokinase, UDP-glucose pyrophosphorylase, and phosphoglucomutase-were observed in all endosperm tissues tested. Aleurone cells predominantly expressed mRNAs for the TCA cycle and oxidative phosphorylation. This finding was supported by the presence of oxygen (8 % concentration) and large numbers of mitochondria in the aleurone layers. In contrast, oxygen was absent and only a few mitochondria were observed in the starchy endosperm. Genes for carbon fixation and the GS/GOGAT cycle were expressed highly in aleurone cells compared to starchy endosperm. CONCLUSIONS: The transcript level of AGPL2 and AGPS2b encoding ADP-glucose pyrophosphorylase appears to regulate the asynchronous development of starch granules in developing caryopses. Aleurone cells appear to generate, at least partially, ATP via aerobic respiration as observed from specific expression of identified genes and large numbers of mitochondria. The LM-based expression analysis and physiological experiments provide insight into the molecular basis of the spatial and nutritional differences between rice aleurone cells and starchy endosperm cells.

Characterization of a novel flooding stress-responsive alcohol dehydrogenase expressed in soybean roots.

Alcohol dehydrogenase (Adh) is the key enzyme in alcohol fermentation. We analyzed Adh expression in order to clarify the role of Adh of soybeans (Glycine max) to flooding stress. Proteome analysis confirmed that expression of Adh is significantly upregulated in 4-day-old soybean seedlings subjected to 2 days of flooding. Southern hybridization analysis and soybean genome database search revealed that soybean has at least 6 Adh genes. The GmAdh2 gene that responded to flooding was isolated from soybean cultivar Enrei. Adh2 expression was markedly increased 6 h after flooding and decreased 24 h after floodwater drainage. In situ hybridization and Western blot indicated that flooding strongly induces Adh2 expression in RNA and protein levels in the root apical meristem. Osmotic, cold, or drought stress did not induce expression of Adh2. These results indicate that Adh2 is a flooding-response specific soybean gene expressed in root tissue.

Stem hypertrophic lenticels and secondary aerenchyma enable oxygen transport to roots of soybean in flooded soil.

BACKGROUND AND AIMS: Aerenchyma provides a low-resistance O(2) transport pathway that enhances plant survival during soil flooding. When in flooded soil, soybean produces aerenchyma and hypertrophic stem lenticels. The aims of this study were to investigate O(2) dynamics in stem aerenchyma and evaluate O(2) supply via stem lenticels to the roots of soybean during soil flooding. METHODS: Oxygen dynamics in aerenchymatous stems were investigated using Clark-type O(2) microelectrodes, and O(2) transport to roots was evaluated using stable-isotope (18)O(2) as a tracer, for plants with shoots in air and roots in flooded sand or soil. Short-term experiments also assessed venting of CO(2) via the stem lenticels. KEY RESULTS: The radial distribution of the O(2) partial pressure (pO(2)) was stable at 17 kPa in the stem aerenchyma 15 mm below the water level, but rapidly declined to 8 kPa at 200-300 microm inside the stele. Complete submergence of the hypertrophic lenticels at the stem base, with the remainder of the shoot still in air, resulted in gradual declines in pO(2) in stem aerenchyma from 17.5 to 7.6 kPa at 13 mm below the water level, and from 14.7 to 6.1 kPa at 51 mm below the water level. Subsequently, re-exposure of the lenticels to air caused pO(2) to increase again to 14-17 kPa at both positions within 10 min. After introducing (18)O(2) gas via the stem lenticels, significant (18)O(2) enrichment in water extracted from roots after 3 h was confirmed, suggesting that transported O(2) sustained root respiration. In contrast, slight (18)O(2) enrichment was detected 3 h after treatment of stems that lacked aerenchyma and lenticels. Moreover, aerenchyma accelerated venting of CO(2) from submerged tissues to the atmosphere. CONCLUSIONS: Hypertrophic lenticels on the stem of soybean, just above the water surface, are entry points for O(2), and these connect to aerenchyma and enable O(2) transport into roots in flooded soil. Stems that develop aerenchyma thus serve as a 'snorkel' that enables O(2) movement from air to the submerged roots.

Total synthesis and structure revision of the (-)-maduropeptin chromophore.

The proposed structure of the maduropeptin chromophore, the biologically active component of the highly potent chromoprotein antitumor antibiotics, was stereoselectively synthesized but did not satisfy the spectra of the natural product. We demonstrated that the correct structure is diastereomeric, which possesses an antipodal sugar moiety.

Analysis of plasma membrane proteome in soybean and application to flooding stress response.

The plasma membrane acts as the primary interface between the cellular cytoplasm and the extracellular environment. To investigate the function of the plasma membrane in response to flooding stress, plasma membrane was purified from root and hypocotyl of soybean seedlings using an aqueous two-phase partitioning method. Purified plasma membrane proteins with 81% purity were analyzed using either two-dimensional polyacrylamide gel electrophoresis followed by mass spectrometry and protein sequencing (2-DE MS/sequencer)-based proteomics or nanoliquid chromatography followed by mass spectrometry (nanoLC-MS/MS)-based proteomics. The number of hydrophobic proteins identified by nanoLC-MS/MS-based proteomics was compared with those identified by 2-DE MS/sequencer-based proteomics. These techniques were applied to identify the proteins in soybean that are responsive to flooding stress. Results indicate insights of plasma membrane into the response of soybean to flooding stress: (i) the proteins located in the cell wall are up-regulated in plasma membrane; (ii) the proteins related to antioxidative system play a crucial role in protecting cells from oxidative damage; (iii) the heat shock cognate protein plays a role in protecting proteins from denaturation and degradation during flooding stress; and (iv) the signaling related proteins might regulate ion homeostasis.

Cytosolic ascorbate peroxidase 2 (cAPX 2) is involved in the soybean response to flooding.

Proteomic analyses of soybean seedlings responding to flooding were conducted to identify key proteins involved. The seeds were germinated on a spongy matrix for two days, and then subjected to flooding for three days. After flooding, the total number of roots, the length of the main root, the lengths of the lateral and adventitious roots, and the fresh weight of the underground tissues of flooded soybean seedlings were significantly suppressed compared with nontreated plants. To identify the early flooding-responsive proteins, the seedling roots were used for preparing cytosolic and membrane fractions. After two-dimensional polyacrylamide gel electrophoresis and silver staining, 208 proteins were detected, and the levels of 44 were different from those of the control. The expression pattern of 10 proteins among the 44 from six different soybean cultivars confirmed that the 10 were flooding-responsive proteins. One of the 10 proteins was dominantly down-regulated under flooding conditions and was identified as cytosolic ascorbate peroxidase 2 (cAPX 2). Northern-hybridization showed that the abundance of cAPX 2 transcript decreased significantly after flooding, as did the enzymatic activity of APX. These results suggest that cAPX 2 is involved in flooding stress responses in young soybean seedlings.

Cortical Aerenchyma formation in hypocotyl and adventitious roots of Luffa cylindrica subjected to soil flooding.

BACKGROUND AND AIMS: Aerenchyma formation is thought to be one of the important morphological adaptations to hypoxic stress. Although sponge gourd is an annual vegetable upland crop, in response to flooding the hypocotyl and newly formed adventitious roots create aerenchyma that is neither schizogenous nor lysigenous, but is produced by radial elongation of cortical cells. The aim of this study is to characterize the morphological changes in flooded tissues and the pattern of cortical aerenchyma formation, and to analyse the relative amount of aerenchyma formed. METHODS: Plants were harvested at 16 d after the flooding treatment was initiated. The root system was observed, and sections of fresh materials (hypocotyl, tap root and adventitious root) were viewed with a light or fluorescence microscope. Distributions of porosity along adventitious roots were estimated by a pycnometer method. KEY RESULTS: Under flooded conditions, a considerable part of the root system consisted of new adventitious roots which soon emerged and grew quickly over the soil surface. The outer cortical cells of these roots and those of the hypocotyl elongated radially and contributed to the development of large intercellular spaces. The elongated cortical cells of adventitious roots were clearly T-shaped, and occurred regularly in mesh-like lacunate structures. In these positions, slits were formed in the epidermis. In the roots, the enlargement of the gas space system began close to the apex in the cortical cell layers immediately beneath the epidermis. The porosity along these roots was 11-45 %. In non-flooded plants, adventitious roots were not formed and no aerenchyma developed in the hypocotyl or tap root. CONCLUSIONS: Sponge gourd aerenchyma is produced by the unique radial elongation of cells that make the expansigeny. These morphological changes seem to enhance flooding tolerance by promoting tissue gas exchange, and sponge gourd might thereby adapt to flooding stress.