Anthers contain starch and neutral lipids, which have key roles in microspore ontogeny and gametophyte development. In this study, we observed the dynamic changes in starch and neutral lipids in the anther developmental processes of castor (Ricinus communis) by cytochemical methods. Starch grains and neutral lipids presented a regular dynamic distribution during anther development. In young anthers, some neutral lipids accumulated in sporogenous cells, whereas neutral lipids disappeared with microspore growth. At the late microspore stage, starch grains began to accumulate in microspores, and the starch content of bicellular pollen significantly increased after microspore mitosis. At anthesis, starch grains and neutral lipids accumulated in the mature pollen grains. Visible changes occurred in anther wall cells. The epidermis, middle layer, and tapetum were degenerated, and only a single layer of endothecium remained at anthesis. The dynamic variation of starch grains and neutral lipids in tapetal cells was consistent with the changes in microspores and pollen during anther development. All these findings demonstrated that tapetal cells directly interacted with the developing gametophytes. The tapetal cells play an important role in supplying nutritional substances for microspore absorption. Moreover, the endothecium protects the pollen and contributes to anther dehiscence. The results of this study provide a foundation for the further research on sexual reproduction in angiosperms.
This study explored the effects of Ustilago esculenta inoculation on physiological responses (activities of defense and antioxidant enzymes) and chitinase gene expression in male Zizania latifolia “jiaobai” (without U. esculenta infection, with no galls, but normal flowering). Male jiaobai seedlings were injected at the five-leaf stage with U. esculenta suspension, and the impact on transcription of several genes encoding enzymes was examined. Compared with controls, expression of most enzymes was significantly different at 3 or 12 hours postinjection, and most ZlChi genes were involved in the response to U. esculenta inoculation. Fluorescence quantitative polymerase chain reaction results showed that U. esculenta was present in the roots of male jiaobai inoculated with U. esculenta at the shoot tips. Paraffin sections revealed many fungal hyphae in the roots at 15 d after inoculation, but few in controls. The results provide a basis for further study of the responses of male Z. latifolia to U. esculenta infection.
The NAC (NAM, ATAF1/2, and CUC2) family is a group of plant-specific transcription factors that have vital roles in the growth and development of plants, and especially in fruit and kernel development. This study aimed to identify members of the NAC gene (PsNACs) family and investigate their functions in siberian apricot (Prunus sibirica). A total of 102 predicted PsNAC proteins (PsNACs) were divided into 14 clades and the genes were mapped to the eight chromosomes in siberian apricot. The PsNACs of the same clade had similar structures. A synteny analysis showed that the PsNACs had close relationships with the NAC genes of japanese apricot (Prunus mume). An expression pattern analysis of the PsNACs revealed many differences in various tissues and at different stages of fruit and kernel development. All eight PsNACs in clade XI have crucial roles in fruit and kernel development. Seven PsNACs (PsNACs 18, 64, 23, 33, 9, 4, and 50) in clades I, III, VI, VII, and XIII are related to fruit development. Eight PsNACs (PsNACs 6, 13, 46, 51, 41, 67, 37, and 59) in clades I, II, V, VIII, and XIII are involved in fruit ripening. Five PsNACs (PsNACs 6, 94, 41, 32, and 17) in clades I, IV, V, VII, and XI regulated the rapid growth of the kernel. Four PsNACs (PsNACs 50, 4, 67, and 84) in clades I, III, V, and XIII affected the hardening of the kernel. Four PsNACs (PsNACs 17, 82, 13, and 51) in clades II, XI, and IX acted on kernel maturation. We have characterized the NAC genes in siberian apricot during this study. Our results will provide resources for future research of the biological roles of PsNACs in fruit and kernel development in siberian apricot.