Pollination induces mRNA poly(A) tail‐shortening and cell deterioration in flower transmitting tissue

Abstract

SummaryPollination induces many physiological responses in the flower, including deterioration and death in specific pistil cell types. It is shown here that within the style of tobacco, pollination-induced cell deterioration was restricted to the transmitting tissue while the surrounding cortical tissue was not affected. It was distinct from general senescence since exogenously applying the senescence-inducing hormone ethylene, or its precursor aminocyclopropane-1-carboxylic acid (ACC), to the flower or the pistil induced overall deterioration in the entire flower. Furthermore, both pollen tube growth and ethylene action were needed for the entire spectrum of cellular changes associated with this pollination-induced transmitting tissue deterioration process. It is also shown that pollination-induced mRNA poly(A) tail-shortening for at least three major classes of transmitting tissue-specific mRNAs. As is commonly observed for poly(A) tail-shortened mRNAs, the levels of two of these three mRNA classes decline after pollination. On the other hand, the third class of mRNAs, transmitting tissue-specific ('r'rs) mRNAs, was maintained at a very high level subsequent to pollination, even after substantial poly(A)-tail shortening. TTS mRNAs encode a pollen tube growth-promoting and -attracting protein needed for optimal in vivo pollen tube growth. The specific preservation of TTS mRNAs in the deteriorating transmitting tissue cells suggests that these cells can distinguish molecules needed in the pollinated styles from those that are dispensable, and protect them from degradation. It is suggested that the pollination-induced mRNA poly(A) tail-shortening and cell death are programmed processes suited to the post-pollination transmitting tissue environment. Results showing that ACC is a candidate signal molecule for the pollination-induced mRNA-shortening which is accentuated by ethylene and mediated via a protein phosphorylation-dependent signal transduction pathway are also presented.

Rab11 GTPase-Regulated Membrane Trafficking Is Crucial for Tip-Focused Pollen Tube Growth in Tobacco

“…Expression of GFP-Rab11b(DN) or GFP-Rab11b(CA) Inhibits Pollen Tube Growth in Vivo and Reduces Male Fertility Upon pollination on the stigma, wild-type tobacco pollen grains germinate efficiently, and a majority of their tubes reach the styleovary junction ;30 h after pollination (Cheung et al, 1995;Wang et al, 1996). Direct examination of pollinated pistils ( Figures 6A to 6N) showed that most GFP-expressing (data not shown) and GFP-Rab11b-expressing grains germinated ( Figure 6A), and many of these tubes reached the basal stylar region by 30 h after pollination ( Figure 6C).…”

“…RNA and protein isolation and gel blot analyses followed previous procedures (Wang et al, 1993(Wang et al, , 1996, except that chemiluminescent detection was used for some of the protein blots.…”

Localization of BEN1-LIKE protein and nuclear degradation during development of metaphloem sieve elements inTriticum aestivumL.

“…In addition, DNA ladders were observed during cell death in toxin-treated tomato protoplasts and leaflets, and the intensity of the DNA ladders was inhibited by Zn 2+ [30]. Moreover, certain levels of Zn 2+ inhibit the PCD induced by various stresses on the plant cell [30]. Our research indicated that the change of Zn 2+ accumulation may affect the expression of BEN1-LIKE protein.…”

“…It has been shown that Zn 2+ has a significant impact on apoptosis of plant cells [12][13]30]. We investigated the dynamic change of Zn 2+ accumulation in the development of MSEs (Fig.…”

“…Two Zn 2+ -dependent nucleases from intact chloroplasts of leaves of Oryza sativa in visible senescence were determined, and when their activity increased markedly the plastid DNA degraded [25]. In addition, DNA ladders were observed during cell death in toxin-treated tomato protoplasts and leaflets, and the intensity of the DNA ladders was inhibited by Zn 2+ [30]. Moreover, certain levels of Zn 2+ inhibit the PCD induced by various stresses on the plant cell [30].…”