Transcriptional memory and response to adverse temperatures in plants / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Temperature is one of the major environmental signals controlling plant development, geographical distribution, and seasonal behavior. Plants perceive adverse temperatures, such as high, low, and freezing temperatures, as stressful signals that can cause physiological defects and even death. As sessile organisms, plants have evolved sophisticated mechanisms to adapt to recurring stressful environments through changing gene expression or transcriptional reprogramming. Transcriptional memory refers to the ability of primed plants to remember previously experienced stress and acquire enhanced tolerance to similar or different stresses. Epigenetic modifications mediate transcriptional memory and play a key role in adapting to adverse temperatures. Understanding the mechanisms of the formation, maintenance, and resetting of stress-induced transcriptional memory will not only enable us to understand why there is a trade-off between plant defense and growth, but also provide a theoretical basis for generating stress-tolerant crops optimized for future climate change. In this review, we summarize recent advances in dissecting the mechanisms of plant transcriptional memory in response to adverse temperatures, based mainly on studies of the model plant

Produtividade de alho vernalizado em função de fontes e doses de fósforo / Productivity of vernalized garlic in function of sources and doses of phosphorous

Objetivou-se com este trabalho verificar a influência de fontes e doses de fósforo na produtividade do alho vernalizado (cv. 'Roxo Pérola de Caçador') em solo com baixo teor de fósforo. O experimento foi conduzido em condições de campo no Setor de Olericultura da Universidade Federal de Lavras. Foram avaliadas três fontes de P (superfosfato simples, com 18 por cento de P2O5; superfosfato triplo, com 41 por cento de P2O5 e termofosfato magnesiano, com 17 por cento de P2O5), três doses (200, 400 e 600kg ha-1 de P2O5) e um tratamento adicional, que não recebeu adubação fosfatada. A aplicação de 200kg ha-1 de P2O5, utilizando como fonte o superfosfato triplo, proporcionou maior ganho em fitomassa total de plantas e melhores resultados com relação à produtividade de bulbos comerciais.

The objective of this research was to verify the influence of sources and doses of phosphorus in the productivity of vernalized garlic in soil with low phosphorus content. The experiment was carried out in field conditions in the Horticulture Sector at the Universidade Federal de Lavras. Three sources (simple superphosphate, with 18 percent of P2O5; triple superphosphate, with 41 percent of P2O5 and magnesium term phosphate, with 17 percent of P2O5), three doses (200, 400 e 600kg ha-1 de P2O5), and one additional treatment, that didn't receive manuring with phosphorus were tested. The application of 200kg ha-1 of P2O5, using triple superphosphate provides the best profit in total mass of plants and productivity of commercial bulbs.

Allelic variation at the Vrn-A1, Vrn-B1, Vrn-D1, Vrn-B3 and Ppd-D1a loci of Pakistani spring wheat cultivars

Flowering time in bread wheat (Triticum aestivum L.) is controlled by vernalization and photoperiod response, and earliness per se genes. The genetic basis of flowering time has not been investigated in Pakistani bread wheat. This study was, therefore, conducted to determine the allelic composition at Vrn-A1, Vrn-B1, Vrn-D1, Vrn-B3 and Ppd-D1a loci of 59 Pakistani spring bread wheat cultivars. These cultivars, along with 4 isogenic lines for vernalization genes were characterized with previously reported DNA markers designed for detecting allelic variation at 4 Vrn (Vernalization) and 1 Ppd (Photoperiod) loci. Spring habit Vrn-A1a allele was found in 36 percent cultivars either alone or with spring habit Vrn-B1 and Vrn-D1 alleles. Two wheat cultivars had the dominant Vrn-A1c allele, whereas none of the cultivars had Vrn-A1b. Spring habit Vrn-B1 was the most frequent allele (64 percent) present either alone or with Vrn-A1a, Vrn-A1c and Vrn-D1. Spring habit Vrn-D1 was found in 61 percent cultivars. Vrn-D1 was singly found in 25 percent cultivars and along with Vrn-B1 in 29 percent cultivars. Dominant Vrn-B3 was absent in all cultivars studied. All cultivars except Era had the photoperiod insensitive allele Ppd-D1a. We did not find any association between the flowering time and Vrn allelic composition of the studied cultivars. This indicated that the partial vernalization requirement of cultivars with Vrn-B1 and Vrn-D1 alleles is probably fulfilled during Pakistani growing season. Earliness per se and the photoperiod sensitive loci other than Ppd-D1 need to be investigated to further understand the genetic basis of flowering time in Pakistani wheat.

The conversion of spring wheat into winter wheat and vice versa: false claim or Lamarckian inheritance.

Paul Kammerer, an Austrian biologist, argued strongly in favour of the Lamarkian view on the inheritance of acquired characters. In his most controversial experiment, Kammerer forced midwife toads, which live and mate on land, to mate and lay their eggs in water. Most of the eggs died, but a few (3–5%) of offspring that survived had lost the terrestrial habits of their parents and, by the third generation, they began to develop black nuptial pads on their forelimbs, a character common to water-dwelling species. This experiment is often cited as an example of scientifi c fraud. Recently, however, Vargas (2009) has re-examined Kammerer’s midwife toad experiments and argues that these experiments show signs of epigenetic inheritance. An immediate discussion on this topic has been published in a recent issue of Science (Pennisi 2009). This new analysis reminds us of several recent reports on the inheritance of acquired behaviour adaptations and brain gene expression in chickens, which may have been transmitted to the offspring by means of epigenetic mechanisms (Lindqvist et al. 2007; Natt et al. 2009). It especially reminds us of Trofi m Lysenko’s converted wheat, a situation exactly analogous to Kammerer’s midwife toad. The characteristic of winter wheat is that if sown in the spring it fails to form ears. It has been shown that the capacity to form ears depends on the plant’s passing through a defi nite internal qualitative change. It was Lysenko who coined the term jarovization, which was later translated into vernalization. It is defi ned as ‘the acquisition or acceleration of the ability to fl ower by a chilling treatment’. The characteristic feature of winter wheat is its requirement of rather low temperature for vernalization. The usual duration of the process of vernalization in most winter wheat at low temperatures (0o–10oC) is 30–50 days, depending upon the variety. Once this stage has been accomplished, the plant becomes capable of forming fl owers in favourable conditions. Spring wheat differs from winter wheat in that it does not require vernalization, and is thus able to ear when sown in spring. Winter and spring habit, as a Mendelian character transmitted by gametes, is a hereditary property in wheat. Before 1930, Lysenko had shown that vernalization of winter wheat can be accomplished before it is sown. The process is to allow the grains to take up water and swell, and then to keep them for the required time at a temperature of 0–3°C. The grains are then dried off: they show no signs of germination but when subsequently sown in spring they ear normally, indicating that they have passed the phase of vernalization. This treatment has no effect on the hereditary behaviour of the plants. That is to say, the progeny of the pre-vernalized spring-sown wheat is still winter wheat; if sown (without pre-vernalization) in the following spring it will not form ears (Morton 1951; Lysenko 1954). However, in a series of experiments carried out between 1935 and 1940, Lysenko and his colleagues established that permanent changes in heredity can be induced by appropriate changes in external conditions at the critical period of vernalization. In the earliest experiments, winter wheat was sown in the greenhouse and kept at a temperature higher than the temperature required for vernalization in normal conditions. After 152 days, 30–40% of the plants eared and gave ripe seed, indicating that these plants had succeeded in completing the vernalization stage, although very slowly, at the higher temperature. The seeds were sown and raised again in the same conditions. This time the plants eared in 77 days. A third generation was raised in the same way and gave ears at 46 days. The seed from the three generations that had passed the vernalization stage at the higher temperature was then sown in the fi eld. The experimental plants behaved as spring forms and eared, but the control plants from the original seed material did not ear at all. Lysenko suggested that the later stage of vernalization was the critical period, in which the change would become hereditarily fi xed. Thus, concretely, to change winter wheat.