The oil palm (Elaeis guineensis), a monocotyledonous species in the family Arecaceae, has an extraordinarily oil rich fleshy mesocarp, and presents an original model to examine the ripening processes and regulation in this particular monocot fruit. Histochemical analysis and cell parameter measurements revealed cell wall and middle lamella expansion and degradation during ripening and in response to ethylene. Cell wall related transcript profiles suggest a transition from synthesis to degradation is under transcriptional control during ripening, in particular a switch from cellulose, hemicellulose, and pectin synthesis to hydrolysis and degradation. The data provide evidence for the transcriptional activation of expansin, polygalacturonase, mannosidase, beta-galactosidase, and xyloglucan endotransglucosylase/hydrolase proteins in the ripening oil palm mesocarp, suggesting widespread conservation of these activities during ripening for monocotyledonous and eudicotyledonous fruit types. Profiling of the most abundant oil palm polygalacturonase (EgPG4) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) transcripts during development and in response to ethylene demonstrated both are sensitive markers of ethylene production and inducible gene expression during mesocarp ripening, and provide evidence for a conserved regulatory module between ethylene and cell wall pectin degradation. A comprehensive analysis of NAC transcription factors confirmed at least 10 transcripts from diverse NAC domain clades are expressed in the mesocarp during ripening, four of which are induced by ethylene treatment, with the two most inducible (EgNAC6 and EgNAC7) phylogenetically similar to the tomato NAC-NOR master-ripening regulator. Overall, the results provide evidence that despite the phylogenetic distance of the oil palm within the family Arecaceae from the most extensively studied monocot banana fruit, it appears ripening of divergent monocot and eudicot fruit lineages are regulated by evolutionarily conserved molecular physiological processes.

Waterlogging seriously constrains growth and yields in oil palm. To date, the responsive molecular changes caused by waterlogging in oil palm remain elusive. To elucidate the molecular genetic mechanisms of waterlogging stress, two varieties of oil palm Deli x Lamé and Deli x Ghana were used. The transcriptome profiles of the roots under waterlogging stress and normal conditions were compared via Ion Torrent Sequencing. Four libraries (GNR, GSR, SNR, and SSR) of oil palm roots after 45 days of normal watering and waterlogging stress were constructed. Approximately 6.2 million sequenced reads per library were obtained, with 5.5 million mapped reads (88.64%) similar to the oil palm genome in the GenBank database. A comparison of GNR/GSR showed a high of 3,289 DEGs with most genes up-regulated (1,863 DEGs). The GO analysis revealed the distribution of the DEGs among various pathways, suggesting a wide spectrum of physiological processes impacted by waterlogging stress. Moreover, qRT-PCR showed strong expression of all selected RNA-seq genes in waterlogged Deli x Ghana (GSR), especially GST, SAPK10 and NAC29 that are reported for the time to respond to waterlogging stress. Thus, this study not only reveals the comprehensive mechanisms of waterlogging responsive transcription in oil palm, but also establishes Deli x Ghana as a highly-adaptable variety to waterlogging conditions.

ACC -1-aminocyclopropane-1-carboxylic acid; ACO -1-aminocyclopropane-1-carboxylic acid oxidase; ACO1 -1aminocyclopropane-1-carboxylate oxidase 1; ACS -1-aminocyclopropane-1-carboxylic acid synthase; ACS3 -1-aminocyclopropane -1-carboxylate synthase 3; CAMTA4 -calmodulin-binding transcription activator 4; CEL12 -endoglucanase 12; CML11 -calmodulin 11; CPI1 -cysteine proteinase inhibitor 1; ERF1 -ethylene-responsive transcription factor 1; ERF1B -ethylene-responsive transcription factor 1B; ERF91 -ethylene-responsive transcription factor 91; ERF113 -ethylene-responsive transcription factor 113; bHLH79transcription factor bHLH 79; bHLH94 -transcription factor bHLH 94; HSFA2C -heat shock protein factor A-2c; MYB1R1 -transcription factor MYB1R1; NAC29 -NAC transcription factor 29; PCD -programmed cell death; TCTP -translationally controlled tumor protein; XTH22 -xyloglucan endotransglucosylase/hydrolase protein 22; XTH23 -xyloglucan endotransglucosylase/hydro-lase protein 23; WRKY4 -transcription factor WRKY 4; TF -transcription factor.

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Photoradiation plays a major role in plant growth processes, especially photosynthesis and nutrient uptake. Light intensity and photoperiod affect temperature and caused more transpiration in plants, which influences nutrient uptake. This study aimed to examine the effects of photoradiation on the growth and K, Ca, and Mg uptake of lettuce (Lactuca sativa L.). Lettuce was hydroponically grown in a walk-in growth chamber, and the experiment was performed using eight treatments with eight replications. A combination of eight fluorescent lamps was used to provide a photon flux density of 128±20 umole m-2 s-1 for 15/15 minutes, 45/15 minutes, 345/15+15/15 minutes of black UV, and 345/15+15/45 minutes of black UV of light/dark periods. A combination of ten fluorescent lamps was used to provide a photon flux density of 194±28 umole m-2 s-1 for 30/30 minutes, 15/15 minutes, and 45/15 minutes of light/dark periods and 24 hours of light period. Continuous illumination with higher light intensity gave the greatest shoot fresh weight, plant height and number of leaves. Whereas a shorter photoperiod and lower light intensity gave the lowest shoot fresh weight. Shortened UV light radiation gave better result in lettuce growth performance such as shoot fresh weight, plant height and number of leaves. UV light also damaged the lettuce leaves. The leaves turned brown (brown spot) at the tip of the old leaves. Molar concentrations of K, Ca and Mg in the lettuce leaves were in the order of K > Ca > Mg for all of the treatments. The steep gradient and highest K accumulation at bottom leaves were found at lower light intensity and short photoperiod (15/15 minutes of light/dark). Extended photoperiod improved K and Ca movement and reduced K and Ca accumulation in the bottom leaves. High K in the leaves reduced Ca uptake. Continuous illumination with higher light intensity resulted in the lowest concentrations of K, Ca and Mg. The mole ratio of K/Ca decreased from the top to bottom leaves, whereas the mole ratio of K/Mg tended to be stable except in the treatment with lower light intensity and short photoperoid. The best growth performance was found in the treatment with consistent K/Ca ratio.