Calcium distribution during pollen development ofUncaria hirsutaHavil. (Rubiaceae), with special reference to the function of the protruding oncus

Abstract

Calcium distribution in the developing anthers of Uncaria hirsuta was studied with the potassium pyroantimonite method. The amount and distribution of calcium precipitates change along with the developing anthers and pollen grains in U. hirsuta. Calcium distribution is closely correlated with the anther wall differentiation, exine and intine formations. In mature pollen grains, abundant calcium is in intine, protruding onci and nucleus. A generative cell has more calcium than a vegetative cell does. The calcium storage is likely to contribute to pollen germination, and mitosis of the generative cell. Ubisch bodies formed at the same period with the pollen exine development, and some of them are in close contact with the exine. Abundant calcium is present in the Ubisch bodies, protruding onci and tapetum. These results might support the idea that Ubisch bodies and protruding onci participate in calcium transportation during pollen development. The protruding oncus is likely to have function of calcium or other ions transportation, although further experiment and additional data are required to confirm this. The present study also provides confirmatory evidence to the previous knowledge that calcium participates in regulation of cell differentiation, degradation in each layer of anther wall cells, and pollen development.

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

“…In addition, lipidic material, which may be classed as pollenkitt (El-Ghazaly et al, 2001; Edlund et al, 2004), is deposited onto the exine surface at the late BCP stage. These ontogenetical features were also described in the available ultrastructural studies in Rubiaceae (Hansson and El-Ghazaly, 2000; El-Ghazaly et al, 2001; Kuang and Liao, 2015). …”

Calcium and cell wall dynamics during microspore embryogenesis and double haploid production in rapeseed and eggplant

“…Other studies, using absolutely different approaches and species Kong and JIA 2004;Kuang and Liao 2015;Qiu et al 2009;Wei et al 2015), consistently showed a clearly cytoplasmic signal, which counts in favor of this notion, too. Thus, we can assume that in in vivo microspores, the signal we observed corresponded to cytosolic Ca 2+ .…”

“…In lettuce and oil tea, a progressive increase during microsporogenesis, a decrease during vacuolation, a second increase in young pollen grains, and a final decrease in mature pollen was described (Qiu et al 2009). In Uncaria hirsuta, calcium precipitates increased as microsporogenesis proceeded, with a peak in bicellular pollen and a decrease in mature pollen (Kuang and Liao 2015). In tobacco, calcium was detected in the cytoplasm and nucleus of vacuolated microspores and bicellular pollen, decreasing at late pollen stages ).…”

“…The dynamics of Ca 2+ accumulation during the in vivo process of microsporogenesis and microgametogenesis seems to be different for every species Kong and JIA 2004;Kuang and Liao 2015;Qiu et al 2009), but the sharp peak in vacuolate microspores and young pollen is not only observed in B. napus, but also in other highly responding species such as tobacco ). Our observations suggest that this particularly high Ca 2+ level just at the stages more suitable for embryogenesis induction could be related to the microspore embryogenesis ability.…”

“…Our results confirmed it, since we were able to detect an intense signal within microspores and pollen grains. As to the presence of FF signal in the exine of mature pollen, it could be due to the presence of other, mature pollen-specific PMEs, or to the contribution of the senescing inner anther wall layers which, together with the release of calcium Kuang and Liao 2015;Qiu et al 2009) and of partially and non methyl-esterified pectins to the locular fluid , could be delivering pectin-associated PMEs.…”